MASSACHUSETTS
I.NSTITUTE
LINCOLN
OF
TECHNOLOGY
LABORATORY
IONOSPHERIC BACKSCATTER OBSERVATIONS
AT MILLSTONE HILL
J. V. EVANS
Group 31
,
,
/
?
,.+
,_2
LEXINGTON
_-.
TECHNICAL REPORT 374
.~ -=-
-. i
.
=--22 JANtiAliY 1965
_1
i- *
_
MASSACHUSETTS
E-
-
ABSTRACT
Studies of the electron-density,
of ground-based
ontenna
e Iectron and ion temperatures
radar observations
directed
vertical
O? the M; I I stone Hi I I Radar Observato~.
Iy and o 2. 5-Mw
these measurements which were conducted
throughout
1963.
tron de.si~
Examination
with height,
pulse radar
operating
the electron
measurements of the spectra of the signals corresponding
Tefli
to be determined
corrected
for the effect
Re%ulk of observations
presented.
soon after dawn,
ratio
extending
The ratio
throughout
Te/Ti
irrespective
the daylight
At night
remained
in the temperatures
5W
Te/Ti
considerably
affects
independent
of height above
magnetically
disturbed
Accepted
Sto”ley
for the fir
o maximum
of the season.
There
at .11 heights.
-2.0
was I ittle
employed
intervals
leads to a profile
of elec-
are the some (Te = Ti).
Addi-
heights permit the ratio
the observed profile
iv
for
co” the” be
in temperature.
1963 to Jon”aV
1964 ore
to 2.6 at o height of abut
change in height
dependence
300 km
in this
fel I with a time constant of the order of
but more often a significant
Ion temperature
increased
with
difference
height at all
times,
due in part to the presence of an unknown amount of He+ ions, which
the interpretation
about
condifio”s,
of the signal spectra.
300 km.
Evidence
Electron
temperatures
is presented of ionospheric
were
largely
heating
during
b“t it is show. that this is only of great importance
Force
Lakr.tov
volue
close to unity,
USAF
Lincoln
by the ineq.al
parabol i.
weekly
to different
from unity,
hours, and at sunset the ratio
J. Wisniewski
Lt Colonel,
Chief,
introduced
was occasionally
km this may &
of height
over a period of one year from Febr”o~
achieved
on hour.
b“t akve
this is different
on the scattering
A 70-meter
at 440 Mcps were
and ion temperatures
tional
and, where
were mode by means
for periods of 30 hours at approximately
of the echo power as a function
provided
in the F-region
Office
111
at night.
I
TABLE
OF
CONTENTS
111
Abstract
I.
i
INTRODUCTION
2
11. THEORY
A,
Electron-Density
B.
Signal Spectra
C.
Electron
Cross
D.
Mixtures
of Ions
2
Distribution
3
4
Section
4
5
111. EQUIPMENT
IV,
V.
VI,
VII.
VIII,
IX,
X.
XI.
XII.
A,
General
5
B.
Receiver
5
C,
Echo Power
D,
Spectrum
OBSERVING
b
Integration
Analyzer
6
PROCEDURES
7
7
A,
General
B.
Choice
of ~lse
Length (Profile
C.
Choice
of Rise
Length
DATA
Measurements)
(Spectrum
Measurements
Profile
B.
Spectrum
8
9
ANALYSIS
A.
8
9
Measurements
9
Measurements
RESULTS
I*
Measurements
ii
ACCURACY
OF
A.
Profile
B.
Spectrum
12
Measurements
OBSERVATIONS
13
IN i963
13
A,
General
B,
Reduction
13
Procedure
ELECTRON-DENSITY
ION-TEMPERATURE
i7
MEASUREMENTS
ELECTRON-TEMPERATURE
MEASUREMENTS
TEMPERATURE
15
MEASUREMENTS
MEASUREMENTS
OF ELECTRON-TO-ION
RATIO
!8
+8
DAYTIME-TEMPERATURE
XIII.
AVERAGE
NIGHTTIME-TEMPERATURE
XIV.
TEMPERATURE
MAGNETICALLY
EFFECTS
ASSOCIATED
WITH
DISTURBED
CONDITIONS
20
XV,
SCALE
OF UPPER
2*
XVI.
HEAT
XVII,
XVIII,
HEIGHT
FLUx
BE~VIOR
i9
AVE~GE
F-REGION
BE~VIOR
20
23
Q350
24
DIsCUSSION
A.
High Values
for Electron
B,
Ionospheric
Anomalies
Temperature
24
25
26
CONCLUSIONS
iv
IONOSPHERIC
BAC~CATTER
OBSERVATIONS
AT MILLSTONE
1.
HILL
INTRODUCTION
In recent
impetus
the study of the upper part of the earth’s
years
from the development
of electron
density,
side sounder Alouette.
concerntig
believed
the behavior
that,
heights.
and rocket methods of exploration.
results
have been obtained with the satellite
In addition,
the rocket
success ful.$
study of the drag on satellites
produced
measurements
Partly
as a result
by tbe neutral
of this region
above the peak of the F-region,
+ Ti)/mig
In this model,
= 2kTi/mig,
experiments
supported
consequence
of observations
sist of regions
the proton distribution,
until heights
The results
upper F-regiOn
is interpreted
sounder
electPOn density
constant
this satellite
icant role
@er
in governing
these regions,
over
equal
controlled
by
height
and mi is the mass of atomic
with height,
and some rocket
complex
as a
parta of the ionosphere
con6-9
(b) the electron and ion
between
0+ and H+ (Ref. 45)
of the separate
constituents
may not
lb
Alo”ette
indicate
scale
height
anomaly
that very
H (Refs.
of the above effects
has shown that the equatorial
into the upper F-region
i9 and 20),
this control
exhibit
that one or more
Te were
has given way to one more
equilibrium
of 700 km are reached.
ideas
a wide range of
with a scale
exchange
Vir -
from the
it was widely
was wholly
ions predominate,
(c) charge
and diffusive
ion over
comtant
Island,
early
recently
distribution
significantly
and the top-
and partly
with altitude
(a) the uppermost
obtained by the topside
as indicating
sondes extends
(Refs.
which show that:
in which helium and hydrogen
be established
addition,
to vary
This model
this prediction.
Wallops
of the ions Ti and electrons
k is Boltzmann’s
need not be the same, ‘o-i4
temperatures
governs
where
H is not expected
Ariel
constituents,
Until very
0+ was the principal
and independent of height, and that the electron-density
diff”~ion2-5
Thus the electron density would decrease
H = k(Te
made from
atmospheric
considerable
In the measurement
of this work,
have been abandoned.
It was also thought that the temperatures
oxygen.
has received
of satellite
outstanding
ginia have been particularly
ionosphere
others,
17 and is).
operate
observed
a range of geomagnetic
and possibly
rarely
does the
This result
at most latitudes.
with ground-based
latitudes
the geomagnetic
of at least
field
In
iono -
+20”
plays a Signif-
the electron-density
distribution.
Theoretical
attempts to account for
21-24
b“t it cannot yet be claimed that all the features are
been made,
have recently
understood!9
At high latitudes
particles
fore,
geomagnetic
may contribute
to the ionization,
that only in temperate
geomagnetic
control
control
latitudes
of diffusion
may disappear
particularly
is the F-region
or additional
sources
b“t significant
in the auroral
likely
fluxes
zones.
to be largely
of ionization
from
of precipitating
It seems,
uninfluenced
the Van Allen
thereeither
by
belts.
-. —-.
In these latitudes
derived
from
functions
an understanding
observations
of height:
composition;
incident
(a) electron
dependence
radiation.
At the present
of, for example,
method
from
involved.
(d), but betig
Further,
involving
inexpensive
is the radar
considerable
ground-based
a radio
incoherent
in order
to observe
effort
method it is insensitive
backscatter
technique
in-
the separate
first
by Bowles 27, 28 and later by Pineo.
form
came into operation
results
of the first
year of operation.
account of tbe incoherent
is provided
procedures
in January
in Sec. 111, the observational
are presented
more
variations,
measurements
repeated
by Gordon
of tbe quantities
(e) through (h). This
26
and employed to
@ g. 29, 30 The backscatter
1963. and this report
In Sec. 11 we review
backs catte r radar
simultaneously
temporal
to the quantities
discussed
in its present
reduction
are being measured
and expenditure.
method can provide
facility
Observatory
(d) ion
and (h) the
these data to extract
study the ionosphere,
A detailed
as
the electron temperature
on height, local time, latitude (and longi25
Thus,
rockets appear to provide tbe best means of makflux.
are required
relatively
(a) through
composition;
many of these quantities
but it is often difficult
could perhaps be
simultaneously
(c) ion temperature;
(g) neutral
but so far none bane been equipped to measure
of the quantities
launchings
@e
temperature;
temperature;
time
F-layer
are measured
in the solar
ing these meas”reme”ts,
than three
of the ionospheric
quantities
(b) electron
(f) neutral
by means of satellites,
tude) and variations
rocket
density;
(e) neutral density;
solar
dividually
of the behavior
in which tbe following
briefly
facility
the theory
the
of the method.
at the Millstone
methods
presents
are presented
Hill Radar
in Sec. IV,
and
in Sec. V.
11. THEORY
A.
Electron-Wnsity
In i958,
ionosphere,
intensity
Gordon
pointed out that if a very
a weak but detectable
cross
section
confusion
has arisen
unit solid
angle,
echo from
the free
by assuming
m= given by the square
because
powerful
this cross
section
radar
beam were
electrons
there
that the electrons
of the classical
is defined
directed
at the
might be obtained.
s tatter
radius
The
independently
with
re = (e2/mC2).
as that which scatters
energy
Some
into
in radar calculations,
it is customary to normalize
the cross section
31
Hence the radar cross section Ue is
reflected
tito 4X solid angle.
-28
2
to be 4UUC (-10
m ). For a volume contatiing
N electrons,
tbe phase of the N re-
to correspond
expected
26
of the echo can be computed
~ ~cattering
flected
Distribution
whereas,
to power
waves will be tidependent
~oportion.1
to Nve.
Because
and the powers
should add to give
at any given height the electrons
an average
completely
scattered
power
fill the radar
beam,
the echo power should vary with range R only as i/R2, not i/R4 as for conventional (i. e.,
,,point !,) target S, For observations
conducted in the zenith it may be shOwn that the echO Power
PT is given i“32-34
(i)
where
Pt is the transmitter
is the velocity
the plse
antema
of light,
center.
pattern
G(e)
power,
Vr is the efficiency
T is the pulse length,
is the antema
is cyltidrically
wave~ide
A is the radio wavelen~h
gain overa
symmetrical
of tk
lossless
about its axis,
isotropic
and e
or feeder
system,
c
and h is the height to
radiator,
assuming
is the angle subtended
that the
in any
direction
from
reasons
The electron
this axis.
which will
can be reduced
be given.
cross
For a t~ical
A.
0.74
is the effective
however,
(2)
One of the largest
more
to detect
nearly
B.
was first
a signal
density
were
Ah = cr/2,
aperture
Puerto
If,
one has no choice
but to
to obtain useful
results.
A.
Rico)
employs
the same
but has a value of Ao which is 20 times
independent
higher
of height,
than Millstone,
the Arecibo
but in practice
radar
that
could be
this ratio
Bowles
in which it is assumed
correctly
x is greater
ofxD),
than *AD,
When the radar
The motions
wavelength
when observations
magnetic-field
signals
will be
was consider-
that each electron
of its velocity
in a
this behavior to the role played by the ions
36
and others37-39 ha”e shown that when
by Fejer
ID isthe
where
Debyele”gth
(=-),
by one in which the collective
behavior
of the ions govern
in the electron
is significantly
centers
to the component
attributed
papers
and these fluctuation.
be thought of as the scattering
complex
of the scattering
shift proportional
above must be replaced
and ions is considered.
(with a scale
width of the reflected
Subsequent theoretical
the radar wavelength
model
that the Doppler
for a model
with a Doppler
to the radar.
in the plasma,
more
(at Arecibo,
Hill radar,
four times
to discover
ably less than expected
simple
effective
of a
PtTAo.
Spectra
28
contributes
direction
can adjust only the product
two times
5ignal
Bowles
Pt and large
so far constructed
echoes
Eq. (2) we see that, for the detection
designer
given height resolution
power
Pt as the Millstone
If the electron
at Millstone35
expected
systems
power
From
h, the radar
to obtaina
both a high transmitter
transmitter
‘
antenna aperture.
N at a given height
it is necessary
employ
different from we = (4uuC) fOr
33
has ahown that Eq. (i)
Evans
2
‘tV r c ‘NoAo
16nh2
given density
u is usually
antenna,
to
P==
where
section
parabolic
.Onstitute
larger
fluctuations
small
changes
than the size
and not the individual
are conducted
density
in the refractive
index
of these fluctuations,
electrons.
in directions
the
of the electrons
normal
they must
The situation
or nearly
becomes
normal
to the
for then the gyrorotation
of the ions causes the ion motions to be ordered.
40
andothers?i-44
._ experimental
and
verification
of the
This case has been considered by Fejer
narrowing
lines,
of tbe spectrum
part in observations
In the theory
at the Millstone
de”eloped
energy
distributions
further
assumed
hence,
E“ans
It is clear
of both the electron
the shape of the spectrum,
from
of the spectrum
and Pineo
and Loewenthal,
effects
they will not be discussed
that both electrons
and maybe
from
this fipre
temperature
tbe ratio
T,
Te/Ti
play no
further
here.
and ions ha”e Boltzmann
neglected.
ions of mass mi are present,
mi is known then Ti can be obtained
observatio,>s
11
by Evans
are infrequent
charged
shown in Fig, t.
is a function
by PineO> e~ ti. 45 As magnetic
Hill observatory,
36.
.
~t IS assumed
and that collisions
by determining
addition,
by Fejer
that only singly
spect run] takes the form
quency spectrum
has been reported
Then,
if it is
the shape of the echo
that the echo power
and ion temperature
Ti;
can be determined.
If,
the total width of the spectra.
fre-
in
The first
shapes from which these quantities were efiracted
were reported
42
Subsequently,
further measurements
have been repel.ted by
and Hy,lek.
46 and ~van~,47,48
3
C.
Electron
The cross
Cross
Section
section
of the electrons
and, as such, depends
and others505’
u is proportionaltO
Bunneman gives
for
the area under the curve
This dependence
upon the ratio Te/Ti.
has been considered
in Fig
1
by Bunneman
49
u the exPres$iOn:
(3)
Thus,
for very
short wavelengths,
being studied by this technique,
for these radars
I >4mkD.
~ = ~e{i/[i
and thus the highest
is a = 0.50e(=
If Te/Ti
from
error,
when i >> 4r~D,
,
cross
that can be expected
section
(4)
of altitude
and some published
b,
at 398 Mcps,
In tbe measurements
of the radio waves
from
by simultaneous
from which Te/Ti
of interest
above
to be described,
and N(h) obtained
accomplished
profiles
of thermal
equilibrium)
of electron
was not immediately
are now thought to be in
34
Q Q.,
and GreenhOw,
an elecfron-density
in place
Eq. (2) by determining
own right,
density
at 50 MCPS,
profile
of the echo power.
~00 Mcps where
measurements
N(h) can only be determined
complication
the echo power
from
the amount of rotation
the variation
The height dependence
corresponding
of Te/?i
is devoted
is
is small.
as a function of
Of u with height.
spectra
and much of the report
measure-
This technique
Pr has been obtained
of the signal
can be obtained.
in their
profile
This
to adopt a method of deriving
at frequencies
to implement
the electron-density
of o is knOwn.
backs catter
difficult
course,
(under conditions
has caused Bowles, 52 operating
rotation
heights
and
0.499 x 40-28~2).
is a function
ments of the Faraday
height,
presently
Eq (3) becomes:
+ (Te/Ti)]}
This difficulty
operating
at heights
the Debye length ID is Of the Order Of a few millimeters,
Eq. (2) if the height dependence
recognized
In the ionosphere,
4nxD ‘> x, u + ne
This
is
to different
and Ti are,
to observations
of
of
these quantities.
D.
MWtures
of Ions
As the ion mass mi e“te~s
0;,
N;
and NO+) could be considered
not be possible
experimentally
pected that significant
the experimental
Observations
conducted
upper limit
ione become
siderably
required
‘
However,
important
one from
of several
to determine
at the Millstone
1/2, it seems
purposes
as identical,
the other.
the ratio
limit
that 0+ and N+ (0’
about 200 km it is ex53
has considered
and Petit
of the heavier
during
in that it would
Below
to the lighter
1963 are restricted
is set by ground clutter
ions.
to a height
ecboes,
and the
Over much of this height range 0+ is expected
to
abo”e
about 750 b
by day and perhaps 500 km at night, H+ and
56, 57
Their presence can modify the scattering conconstituents.
by changing the shape of fhe signal
that the presence
(mi)
of these ions exist,
Hill observatory
The lower
of the signals.
ing the amount of He+ in an O+/He+
lt is clear
for all practical
200 to 750 km.
b#4t~5 strength
predominate.
in the form
to distinguish
concentrations
accuracy
range of approximately
H:
the equations
of large
mitiure
specfra.
Fi~re
2 shows the influence
on the shape of the spectra
amounts of He+ (e. g., 50 percent)
of increas -
for the case Te/Ti
can be recO@ized
= 2.0.
readily.
However,
if only small
cating an erroneously
how the quantities
be etiracted
analysis
at higher
spectrum
and lower
consider
pulses,
Ti and the ratio between
that:
and (2) it is possible
the spectra
high value of Ti and low value
Te,
from
provided
amounts of He+ are present,
to remove
some ambi~
In practice,
also the distortion
and in any radar
of the filters
employed
these effects
for the Millstone
there
it is possible
ities
pulsed radar
spectra
analyzer.
Observatory
Observatory
is located
has considered
to perform
such an
of precision;
by observations
observations
conducted
are made one must
by the finite width of the transmitter
smoothtig
Considerable
Hill Radar
as indi-
H+ and O+ ions might
high degree
in the interpretation
where
will be some further
in the spectrum
of He+,
can be made to a very
of the theoretical
system
Moorecroft58
the percentages
In principle,
observations.
(1) the measurements
altitudes.
of Te/Ti.
might be interpreted
due to the finite
effort
width
has been made to compute
(Sec. V).
111. EQUIPMENT
A.
Generti
The Millstone
42.6”N).
Hill Radar
The parameters
is a 70-meter
parabola
of the ionospheric
directed
junction.
allowing
any mode of polarization
one sense
A pair of opposite
are transmitted
fourth port.
B.
and receiver
frequencies
from
in Table
into remotely
shorts
polarized
waves
of
is coupled to an-
is similarly
are controlled
frequency
horn coupled to a
adjustable
circularly
and the receiver
(7i.5”W,
The antenna (Fig.3)
The transmitter
received.
frequencies
a single
I.
is a circular
In practice,
sense
Massachusetts
coupled to the
by synthesizing
all the
standard.
Receiver
The first
amplifier
is synchronously
in the receivers
twice
a Zenith
pumped (at 880 McPs).
due to an unwanted side-band
precisely
are connected
junction by a wave~ide,
The transmitter
needed oscillator
ports
to be radiated.
and the opposite
other port of the turnstile
are listed
The feed system
vertically.
turnstile
radar
in West ford,
the radar
or image.
frequency
electron-beam
This amplifier
However,
(i. e.,
hy employing
synchronously
TABLE
PARAMETERS OF
Polarization
Circular
A
0
UO Mcps
Transmitter
power Pt
2.5
Transmitter
pube
0. 1-,
Receiver
frequency
bandwidth
System temperature
Post detector
b
T
s
integration
which is
can be removed.
RADAR
1600 m2
f
P“lse repetition
tbe image
which
noise
fixed parabola
Frequency
lengths 1
amplifier
additional
a pump frequency
pumping),
IONOSPHERIC
70-meter
aperture
introduces
I
Antenna
Effective
parametric
normally
Mw
0.5-and
l. O-msecp”lses
used
50 Cps
25 kcps
-200”K
-20
(monitored
continuously)
db
5
.,..,
—
.... -----------
Unfortunately,
the phase information
sible to observe
amplifier
tical
at the output of the receiver
now operates
fluctuations
after
of the signal
is then destroyed;
if the signal
both in the conventional
samples,
amplifier
fluctuation
with system
by the rapid recovery
following
plete stability,
and the fact that it cannot be destroy ed by moderate
The statis-
are also changed so that,
T3.
are outweighed
impos-
for the
exchanger.
is +&TB/&
temperature
of the amplifier
it becomes
is asymmetric,
of the receiver
the rms temperature
as in the case of a conventional
spectrum
way and as a side-band
of the noise at the output terminals
n independent
that is,
instead
These
of*T~/~n
disadvantages
the transmitter
pulse,
its com-
amounts of transmitter
power.
C.
Echo Power
Integration
The electron-density
profiles
are obtained
a function of height is determined.
whose bandwidth
(25kcps)
flected
si~al.
voltage
proportional
at intervals
is sufficient
ing these voltages
is achieved
sampled
The signal
spectra
analog integrators.
off,
are explored
the detectors
bandpass
20db
for periods
(to *3-K).
Fig-
of 100psec
(45 km)
intervals
and interlacing
to the filter
bank.
scheme
characteristics
channels,
This second
set stores
restrictions
with a half-power
which is normally
spectrum
stigle -pole
is being explored.
and to remove
any influence
a second gated POTtiOn Of the
is equal in width to the first,
cmbe
before
on the maximum
i963,
are
constructed
and the time at which the trans-
signal
is expected.
in another set
md the second set otiy
elimtiated.
Because
noise;
prf,
width of 500cps
which canotbe
were
this com-
morethm
employed
having
and center-to-center
by
the oscillations
the second pulse is applied,
filters,
but at
The outputs of
to this second gate
plus noise
effects
to decay completely
Throughout
portion
corresponding
si~al
amplifier
the detectors,
which no detectable
the two sets equipment
imposes
filters.
(50-kcps)
this gated portion
to store the voltages
by carefully
equal to the length of the transmitter
on the shape of the spectra..
to a height from
Thus the first
The outputs of the filters
the height at which the signal
of the receiver
must be ~lowed
present
usually
A resolution
are then summed
by a wide-band
t between
the gains of the filter
a ratio between
fortbe
The delay
determines
are switched
of 24 titegrators.
pensation
by at least
voltmeter
represent-
a plot of the integrated
is conttiued
of iOO-psec
by a bank of 24 filters.
are driven
stages
is applied
of the filters
an odd number
numbers
a
intervals.
The filters
a delay corresponding
takhg
period
by a digital
to form
vs delay.
of the re-
which provides
The digital
process
in power
power
and these voltages
to calibrate
time-base
the fluctuation
and gated on for a part of the time-base
of the earlier
is sampled
levels.
in the CG24 computer
detectors,
pulse is radiated
k order
reducing
at 200-psec
pulse (0.5 or 4.Omsec).
mitter
in turn,
components
detector
as
a filter
Analyzer
with linear
switched
all the frequency
This integration
of a plot of integrated
by making the interpulse
Spectrum
rectified
thereby
an example
two time-bases
D.
summed
in the receiver
to a square-law
This voltage,
the time-base.
in which the echo power
by placing
one of 25b possible
and assigned
are continuously
of $0 to 20 minutes,
ure 4 provides
is connected
to the input power.
echo power vs delay over
measurements
to accommodate
The output of this filter
of 200psec
from
This is accomplished
50cps
identical
spactig
of
480 CpS,
Both halves
of the spectrum
would be destroyed
should be identical.
by the receiver.
) Thus,
(Even
if asymmetry
only one half is normally
were
measured
to exist,
and either
it
the
upper or lower
self time
pulses
side band can readily
constant
of several
to the filter
IV.
OBSERV~G
A.
and the 48 stored
by meahs of a i4-bit
are recorded
on a p“ncbed
for spectral
digital
observation
were
usually
hour the equipment
are automatically
These
voltages,
have a
the receiver
sampledin
together
with the
paper tape.
made at intervals
was Observed
was operaiedas
TYPICAL
twice
during anY One run.
shown in Table
EQUIPMENT
Computer
Pulse Length
(msec)
analysis,
thus to explore
in summer,
of each hour,
the RF
15
3.0, 4.0, 5.0
5
(and 6.0)
were
to the
were
to record
transmitter
recorded
antenna aperture
Te/Ti
from
on magnetic
11) normally
D“ring
but in winter
and the measurements
of a signal.
the behavior
more
analysis
rapidly
repeated
as
The vOltage OutPuts
analysis.
at a later
time;
this
than once per hour.
is known (from
the sigml
absolute
power
measurements.
power
Pi,
the transmitter
at nighttime
At the end
on a punched paper tape for later
for spectrum
occupy
the daytime
beyond about 3msec.
in the absence
signals
to determine
Ao,
removed
recorded
an hour.
with a delay of 6msec,
fashion
IF
were
(Table
takes almost
was
in binary
the receiver
temperature
Fig.4)
make measurements
at that height can be determined
spectra),
the electron
These
and the receiver
require
sYstem
tem-
T~ be determined.
Antenna aperture
repositioning
to couplers
is measured
by obser~ing
the radio
of the feed so that the beam is directed
The transmitter
following
obtained
(e. g.,
at anyo”edelay
of the equipment
can be useful when it is required
perature
measurements
strengtbto
operation
If the electron-to-ion
in the computer
the full range of heights
of the integrators
density
(msec)
1.0
It is also possible
that the effecti”e
Spectrum Delay
1.5, 2.0, 2.5
drive
a check on the proper
Integration
15
signal
‘n any ‘ne
SEQUENCE
0.5
useful measurements
was insufficient
OPERATION
10
Spectrum
In
II
o. I
The sums of echo power formed
5 minutes,
Typically,
of
day.
11
(min. )
0
taPefo~later
%963. Each period
near 0900$< and ended at about i700 on the following
commenced
behavior
of about one week throughout
TABLE
; “
period,
Generti
this way the da~ime
*Time
voltages
voltmeter.
The integrators
integration
PROCEDURES
Observations
there
analysis.
At the end of a 5-minute
bank are removed
turn and measured
time,
be selected
hours.
power
inserted
way.
is continuously
monitored
into the waveguide.
A gas discharge
periods are EST .nlessothemise
The
tube prOviding
source
in Cygnus A which requires
toward the south by 2“ from
by means of power meters
system
temperature
T~
the zenith.
which are connected
is determined
a 10,OOO”K nOise sOurce
a
in the
is cOupled tO the
indicated.
. .. . .
. .. . . ,“,...
.-.
...”-
recei”er
via a 20-db coupler
A iOO” K rise
in system
output power
TR
cavity,
temperature
vs delay formed
any
been employed
in the noise source
but are usually
in the determination
to differ
profiles
nre assigned
mined,
The ionosonde
of Pulse
The echo power
profile
represents
profile
the shortest
echo power
is used.
of the F-layer
between
The resolution
the profile,
afforded
with better
gions the scale
Pt.
Hence,
chiefly
have
errOr
for the most part,
the’electrOn
density;
measurements
the convolution
In order
the
instead,
the
in which foF2 is deter-
radar.
pulses
of the shape of the pulse Ah = c~/2 with
to minimize
length
the distortion
compatible
T
Hill apparatus
density
(i5km)
ratio
with achieving
(Fig.
the main features
altitude
Fortunately,
to the pulse length, and serious
sufficient
Tbe thickness
5).
of
are lost.
above 400-km
resolution).
intro-
of iOOkm or more
to explore
the region
(though poorer
of the profile
this is 100 psec.
is of the order
is adequate
pulse measurements
height is comparable
is governed
A comparable
having small height extent (e. g., the PI ledge)
signal-to-noise
the
Measurements)
value of pulse
by iOO-psec
before
such noise sources
of+ldb.
of the backscatter
points of half-maximum
but features
power
temperature
Several
by the order
ionosonde
For the Millstone
Dnring the 0.5- and I-msec
plored
from
N(h).
duced by the pulse,
system
to determine
within Ikm
Length (Profile
the true electron-density
[Eq. (2)]
scale
is located
receiver
isplaced
of the TR tube can be recognized.
of the transmitter
an absolute
in the plot of integrated
If tbe 20-db coupler
used as a reference.
observed
value of the echo power is @used
Choice
(Fig. 4).
the antenna efficiencya”d
absolute
B.
at the end of each sweep of the time-base
can then be observed
in the performance
indetermining
by the uncertainty
for 2msec
in the computer
deterioration
Accuracy
may exist
and ignited
distortion
is ex-
in these
re -
of the profile
is
not introduced.
C.
Choice
of Pulse
Len@h
Tbe height resolution
that for the density
to minimize
(Spectrum
achieved
measurements
the distortion
Measurements)
in the spectrum
measurements
as a consequence
of the spectra.
of the need to employ
For 0.5-msec
pulses
imately
75 km, and the width of the pulse ( 2 kcps ) is of the order
spectra
(iO kcps).
proportionally
wider
A/4ThD wodd
me
operating
and shotier
aPProach
measurements.
low elevation
If a higher
pulses
unity at a lower
solution
frequency
tbe vertical
pulse and the receiver
are received
seems
However,
signal
in this case,
restrict
delay t sec between
the lowest
the vertical
beigbt is (./2)
electrons
distributed
the spectrum
between
the most.
these heights
Actually,
P, which is given this weighting
most delays),
the effective
for this by computtig
echo power
Pr,
by the receiver
center
the effective
in a trianWlar
fashion,
it is not the electron-density
gate.
lower
the ratio
(t + r) km.
at a
of the path.
edge of the
height from
which echoes
The combined
gate is to “weight”
the
those at (c/2) t km affecting
distribution
but the echo power
with delay
than et/2.’
height of the pulse as a function of delay
vs height measurements.
would he
extent Of the
the leading
As Pr is decreasing
of the pulse is somewhat
in order
is approx-
an antenna directed
action of the finite width of the pulse and the equal width of the receiver
than
the width of the
spectra
of tbe pulse by the obliquity
gate (of width r se.),
is (c/2) (t – r) km, and the uppermost
long pulses
of one-fifth
to be to employ
etient
poorer
the height resolution
employed,
could be used.
For a pulse of length ? sec and a spectrum
transmitter
were
height and thereby
of this dtiemma
angle and to restrict
is considerably
AllOwance
t,
t (for
is made
frOm the Obser~ed
V.
DATA
A.
~ALYS2S
ProfUe
Plots
Measurements
of echo power vs delay
the computer
in the following
way.
about 20 points near the center
points.
Mean power
the absolute
level
(Fig. 4) are recorded
First
the mean noise level
of the time–base,
of the noise
calibration
of the echo power.
the electron-density
( Fig. 5).
Smooth curves
eflracted
from
Fi~re
an example
At this point the profile
but, as Fig. 6 shows,
observed
which enables
mated.
when the values
version
kequdity
B.
large.
value of the plasma
to interpret
for Te/Ti
cm be applied
shows the corrected
perature
ustig
These
are applied
to remove
frequency
spectrum
that at ihe center
ratio
frequency,
be allowed
for,
spectra
spectra
!
I
is established
accurately.
of height (Fig. 7), a firstprofile
N(h).
adjustment,
Figure
8
to allow for the tem-
and in order
(e. g.,
of the power
corresponding
have been recorded
between
measurements
Te/Ti
spectra
controls
power
is obtained.
observed
at
Cor-
in each pair.
during the runs
These
necessary
to find which agrees
tbe ratio
(x) is scaled
the center
x between
to compare
best.
as a measure
resolution
spectra
in the receiver.
pulse,
were
Ti.
spectrum
to compute
then cOnvOlved,
and
The effect
analyzer
a large
first
quantity
is also scaled
of the ion temperature
of the receiver
the
in the wing to
A second
from the records.
each
Because
the power
and a point of half peak power,
in the transmitter
to given values
spectrum
the integrators
it is simply
to do this it has been necessary
Fig. i)..
is later
is then taken of each of the
to obtain the signal-to-noise
the signal
differences
this quantity
between
of one of the filters
in Fig. 9,
is
(Sec. IV).
pulse and the frequency
theoretical
these ratios
with a set of theoretical
difference
of the transmitter
response
as a function
by taking a mean of all the ratios
for a given ion mass mi may be regarded
distribution
profile
the value for foF2
scale
measurements
and a ratio
to the 24 noise powers
the spectrum
temperature
the frequency
density
fp at all other heights to be esti-
voltages
are squared
one from
is not radiating
to analyze
electron-to-ion
an absolute
shown in Fig. 6 after
systematic
are obtained
when the transmitter
measured
by assigning
have been obtained
All the values
By subtracting
corrections
In order
Thus,
density,
Eq. (4) to obtain the true density
of the proftie
of the 24 signal-plus-noise
rections
The computer
Measurements
by the computer.
each frequency.
out later.
N(h) if v is a function of height
the spectrum
The punched paper tape on which the 48 integrator
values
to the square
shown h Fig. 7.
Spectrum
analyzed
and used to define
in the same hour.
46
and has been published previously.
profile
is not etiremely
in order
of
all the
pulse observations
from the true profile
to the point of peak electron
the approxtiate
correction
0.5- and i. O-msec
of such a combined
the error
This is necessary
Later,
order
established
from
up in proportion
N!(h) which is printed
by
to the peak value and plots it as a function of height
N? (h) may differ
on the ionosonde
malyzed
from the values
are drawn through these plots by hand, and a single
the plots of the 0, ?-,
6 presents
is established
pulse (Fig. 4) is neti
profile
profile
tape and later
and this mean is then subtracted
Echo power is then scaled
of the height to obtain m electron-density
normalizes
on magnetic
must
number of
with the sPectral
and second with the power -vs-frequency
The effect
of Ti and Te/Ti
of the convolution
is to lower
on theoretical
x and increase
f as shown
f,
effect,
A third
ceiver
sary
gate on the shape of the spectra.
to define
pulse center
the height interval
spectra
However,
distribution
the receiver
are received.
gate is neces -
The effective
height of the
of echo power within this gate, and this quantity
introduced
in the initial
previously,
is the action of the re-
by tbe receiver
theoretical
calculations.
gate in the shape of the signal
From
more
recent
that when the gate width is made equal to the pulse length the spectrum
changed only by a further
fore,
which echoes
the distortion
was “ot included
it appears
As mentioned
from
is defined by a weighted
is calculated.
I
which has not so far been taken into consideration,
that the neglect
lowering
of this effect
of the wing,
and hence the ratio
will not in any way influence
but Te and Te/Ti
may be underestimated
tbe experimental
error
by 40 to 20 percent.
is reduced.
the values
computations,
shape is
It seems,
This is probably
hereti,
comparable
up to 500 km and less than the experimental
at most heights
there-
of Ti reported
error
with
above
500km.
The solid lines
in Fig. 9 represent
vations
at a height where the plasma
plasma
frequency
~-),
stems from
the spectrum
charts
for a i-msec
Thus,
at the wavelength
a spectrum
frequency
the fact that,
shape cba”ges
(68 cm) employed
N (which then specifies
an approximate
profile
Figs.
pulses
charts
shapes occur.
The values
that above
here,
%.0-msec
L approaches
This is illustrated
frequency
in Fig. 10 whe~(~~~tr”m
depends upon Te,
This accounts
analysis
pulses
for fp = 3.0, i.5,
by computing
Ti
for the need to obtain
reduction.
fp = 5.0 Mcps,
the
4nA
fp have been superimposed,
the shape of the spectrum
Above
This was tested
Charts
such as
2.0 and 5.0 Mcps,
and
and no further
changes
h >> tihD
the 8pectrum
shapes for fp = 30 Mcps.
that 0+ is the only io” present.
corresponding
dependence
It is possible
for
so far assume
of Te/Ti
and the separate
rapidly,
pulse obser -
The need to specify
wavelen@h
the spectrum
at 2.5 and 5.0 Mcps.
di~cussed
to 5 Mcps.
.
tbe Debye length).
performing
9 and 10 have been prepared
in the spectrum
All
before
chart used for i -msec
fn is close
as the radio
pulse at 2.5- and i .O-MCPS plasma
and tbe density
for 0.5-msec
analysis
to the measurements
of Te and Ti on this occasion
500 h
appreciable
shown in Fig. 6 are shown in Fig. 7,
is shown in Fig. 4*.
amounts of He+ were
present
at the time these
The distribution
of He+ ions has been discussed on theoretical
measurements
were made.9
56, 57
grounds,
but unfortunately there is inadequate experimental
evidence at this time to verify
the accuracy
of these models.
What evidence
@ ~. 59 find a complete
Gringauz,
The theory 56 and the experimental
At no time during tbe course
definitely
heights
perhaps
indicate
as much
measurements
spectra
from
results
of Taylor,
of the backscatter
the presence
(750 km by day,
of He+ ions,
as 30 percent
He+ might
cOmputed fOr a plasma
of He+ requires
He+.
containing
Unfortunately,
a Significant
timge
shown ti Fig. i2, it is not possible
namely,
(i)
cent He,
Te/Ti
wholly
0+,
= i.4,
Te/Ti
(Fig. 2),
Fi@re
ioo percent
in the interpretation
of even small
ad
two extreme
(2) 80 percent
titerpretations
aS
amounts
In the specific
between
divergtig
and
with theoretical
0+) Or One containing
of the results.
Ti = 2040”K,
These
ratio,
12 shows that the
the presence
experimentally
Te = 2320”K,
for the uppermost
height are consistent
as Fig. i3 shows,
Ti = i410” K.
obtained
transition.
been obtained that
due to the low signal-to-noise
be undetected
nO He+ (i. e.,
as
520 to 620 km.
a mOre gradual
have spectra
though the spectra
equivalent
contradictory
the height range
& =.9 indicate
measurements
to distin~ish
= i.i4,
Te = i960”K,
is somewhat
0+ to He+ over
500 km by night) are uncertain
made on 2 July at 720-M
much as 20 percent
is available
transition
example
cases.
0+,
20 per-
are tidicated
10
,..
“.,...
——..,:
___
._=.s.J.a,._o,,
z.,.._-..
On a theoretical
analysis
of the behavior
F-region,
it is possible
to decide
Bowhill!”
who have performed
is the very
high thermal
is expected
to be isothermal
between
such an analysis,
conductivity
of the electron
temperature
aPPear
to be c108e8t to the true situation,
Te is isothermal
at the greatest
~ principle,
of tbe slope
described
here,
this slope
filter
spectrum
Tn,
VI.
A.
severe
first
Unfortunately,
profiles
presence
to heights
of He+ ions.
from
of
Despite
the neutral
Either
bane suggested.
and Hanso”63
from
the results
a cure were
unless the malfunction
always
tubes as they aged.
accuracy
to determine
totbose
whether
The random
errors
heights
the recovery
error
shomin
Fig.8.
severe,
Tb”s
of measurement
increase
the echo power is obtained
Alouette
abo”e
However,
pri-
500-km height.
of changes
it is believed
tbe “alues
rapidly
has
An example
(Van Zandt,
was not recognized
for a gi”en
until October.
in the charac-
that the density
prio?to
October
day were
accurate
for the density
above
pro-
it was not
or not,
500km
caution.
with height (Fig.5)
as the difference
to place the
of the TR tube trouble
as a result
with some
of
obtained on 12 July is compared
sounder
Since October,
N(h)
because
(50kcps)
with height.
is enco””tered
or not the results
was particularly
profile
difficulty
short-lived
pulses)
of the TR tube and the
the effect
of the topside
during
has been very
I-msec
sufficiently
of N(h) which increases
due to
not recognized
made in i963 suffered
off-tune
in Fig. 14 i“ which a backs catter
to effect
is usually
Vrhen this malfunction
N’ben not too severe,
underestimation
measurements
by the fact that (for
the recei”er
It can be seen that se~ious
of the discharge
possible
echo.
by day and about 350km at night should be accepted
I
b2
this condition
the fact that this was a continuing
attempts
uppermost
in the re-
corresponding
of the profile
was made to monitor
by switching
obtained
are of comparable
always
filters
of height above 300 km (Ref. 61).
Many of the measurements
pass band.
is given
cur”e
“ate comm””ication),
files
measurement
by the transmitter
with height as distinct
during the course
in the analyzed
provision
the receiver
of this behavior
Earlier
on the
show that
h the measurements
introduced
of the spectra
markedly
Unfortunately,
near 700km.
been to cause a systematic
teristics
(Fig, 2).
time owing to the likely
by the ionospheric
recognized
In October,
with a density
O+/He+ by careful
by the distortion
thought to be independent
have occurred
of the receiver
echo outside
the results
can be minimized.
at the present
of the TR tube.
negative
stages
Te
0+) would
where the results
It is hoped that by using improved
that Ti increases
as it is masked
this trouble.
the ratio
or Ti > Tn above 300 km as Dalgarno
errors
it maybe
becomes
Thus,
Measurements
Systematic
poor recovery
parameter
of Ti or the
(iOO percent
of analyzing
and
OF RESULTS
Profile
an operation
to determine
this problem
which is widely
ACCURACY
of the behavior
of Fig. ii
to be in order,
it may be said that the interpretation
this view is incorrect,
Geisler
heights.
characteristics.
Fig. 11 shows clearly
temperature
curve
near the point of half peak intensity
more than 500km is uncertain
this,
in the upper
about 400 to 500 km.
irrespective
and the restriction
has been set largely
analyzer
w summary
gas abo”e
the solid
may be deemed
It should be possible
of the spectrum
pulse and receiver
ceiver
If this is correct,
that 0+ predominates
and ion temperatures
curves’ shown in Fig. ii,
show that by far the most important
above this height almost
neutral
assumption
Tn.
of the electron
the two possible
between
because:
two large
(1) at the
uncertain
numbers,
(h)2.
and (2) in computing
The profile
filter,
measurements
thus they can always
unusable,
Thus,
measurements
profiles
measurements,
sult,
the backs catter
line)
at 720km.
sources
of error
is operating
The agreement
between
of 20 percent
is possible
the interpretation
in profile
measurements.
These
echoes
measurements
at 1295 McPs to explore
B.
Spectrum
the region
measurement
are averaged.
of samples
percent).
will be &times
are later
f,
(*i
scaled,
times
(Fig.
restrict
radiation
these echoes,
(full
measurements
the antenna feedhorn.
but the resolution
this region,
results
one of the major
the lowest
from
as
to <:4 and, as a re-
with the rocket
can constitute
echoes
shown
in the profile
i2) a,e interpreted
would be raised
completely
in the
obtainable
as Te/Ti,
Ti,
to
It
in the
and the ion
radar
operating
iOO- to 300-km height.
occupies
a period
are stronger
by the uncertainty
When the signal
tbe uncertainty
the determination
since this is a ratio
about fi
measurements
of error
It is planned to use an Oblique incidence
When the signals
in each point is set simply
ratio
wide
are
Measurements
Each spectrum
pulses
with height.
sources
spectra
to explore
ina
measurements
and not by the errors
and backscatter
Te/Ti
are caused by horizontal
would be inadequate
all change rapidly
echo power
to
the upward extent of the profile
of the spectra
ground clutter
in proportion
of thetotal
results
no serious
curve would be adjusted to agree
Evidently
that steps could be taken to reduce
spectrum
mixture
the rocket
there were
He+, the ratio
Below the peak of the F-region,
about 200km.
properly,
of good spectrum
we note that if the uppermost
However,
are scaled
to heights at which the spectrum
by the absence
that on this occasion
tbe presence
these differences
depend ”pon the determination
when the equipment
themselves.
N’(h)
be conducted
is curtailed
in Fig, 8 suggests
indicating
the profile
between
power
more
The error
the error
power
When the spectra
difficult
than the half width
in x might be expected
noise/signal
$5,000
to this number
the signal-to-noise
(i. e., +~per.ent).
x is always
+2 per.e”t
point (i. e.,
(at low heights),
corresponding
is less than the noise,
in the noise level
of tbe ratio
during which time
than the noise
in the signal
two like numbers.
that in a single
of five minutes
powe~ ratio
to be
at low signal
levels).
In practice,
interference
offenders.
when the signal
of various
In the profile
but do not systematically
frequency.
However,
noise ratio
quencies
in an unpredictable
We have already
The poorest
problem
regarded
frequency
spectra
arises,
ratio
fashion
these interfering
are introduced
radars
signals
raise
These
and, as a rule,
they will reduce
interfering
signals
useful spectra
by low-level
appear to be the worst
the absolute
as they are not synchronized
measurements
range.
errors
and search
noise level
to our repetition
the apparent
appear
signal-to-
at different
are “ot obtained
fre-
when the
is less than 0.2.
discussed
the effect
corresponding
At present,
systematic
altimeters
the profiles,
in the spectrum
power
is weak,
measurements
distort
over a limited
signal-to-noise
power
Airborne
forms.
of anion
to the uppe?most
the interpretation
mitiure
on the interpretation
heights
of the spectra
of the spectra.
are in fact those for which this
above 500-km
height must be
as uncertain.
42
—----
.——
W.
OBSERVATIONS
A.
This
report
isintended
results
viously,
together
~ethod,46
Table
ward,
was operated
stage.
Radar
Combinations
all profile
equipment
periods
later
of the remaining
A complete
of the spectra
layer.
Hence,
to present
every
many days’
made during the
and were
III).
reliability
and
the least trouble-
computer
The neti
of results
caused
and, in addition,
mOst seriOus
which resulted
analyzed
frequency
obtained
to the methods
in the loss
during much
to reduce
as 24 separate
in
of
amount
as diagrams
of altitude
of the temperature
in
and time.
is that the equivalent
of changes
in the shape of the
to a given fixed height.
as contours
to prepare
plot.
Thus it has proved
of constant Te/Tp
these diagrams
The diurnal
to study.
Te and Ti on dia-
for each day, hut in practice
over
intervals,
behavior
the results
each calendar
the average
value of the density
the diurnal
month.
plots if records
13
considered
In order
profiles
computing
to do this,
obtained
it is first
the mean shape.
at its peak.
during the equinoctial
of these plots where
averages.
were
to
have been used to con-
and a mean taken of all the results
mean height before
to rapid change (e. g.,
in constructing
make it preferable
ln the case of the electron-density
to their
gaps are left on several
and seasonal
Consequently,
averaged
hourly
a given month.
is subject
this large
plots are presented
are drawn as functions
results
outlined
with the height dependence
In order
time.
the day as a consequence
data info a single
characteristics
can be encountered
according
is obtained together
by loss of data through one cause or another
is then accorded
frequency
meaningful
were
to improve
and time as abscissa.
to adjust all the profiles
Thus,
on-
parametric
of the CG24
interference,
of the accuracy
the diurnal variation
the temperature
in each given hour over
days.
critical
mean plots showing the behavior
mean profile
radio
the electron-density
it would be possible
the day is treated
critical
were
profile
vary throughout
gaps introduced
necessary
in operation
also lost (see Table
hour of observing
height as ordinate
the most important
struct
on-few occasions
any given delay does not correspond
In principle
average
-density
in presenting
heights
the large
incorporated
of the
28 February
in May and June to be destroyed
kinds of etiernal
proportions,
of constant
One difficulty
ha”ing
From
to the equipment
were
errors
weeks
in this program
electron
of data to manageable
convenient
made.
the utility
pre-
Procedure
Te and Ti approximately
grams
occurred
time and in the reduction
The data gathered
which contours
were
and the
time.
Reduction
Sec. V.
failures
in the year were
by various
of some observation
to demonstrate
radar
been published
time.
for eight consecutive
was caused
B.
changes
in Sec. Vhave
pumped electron-beam
modifications
minor
of human and equipmental
results
some shorter
trouble
made in July,
when observations
No other major
cause of lost observing
presented
with” the synchronously
although numerous
performance.
The results
the dates and times
as first
period,
in i963.
with other measurements
111lists
amplifier
to give a full account of the Mi118totie Hill ionospheric
obtained
the recei~er
report
I
1963
General
backscatter
some
IN
The
When the day-to-day
periods),
are missing
some difficulty
for parts of certain
there are insufficient
data to make
C.....!,
,,.
,..
.-”,s
7,sMOr
,,,)5
...
,,m-,7m.. ,4..,,.0 OAT.
(,.”s.;
!.,..!PU”.?:.”1
*V,, MOr
,,. ..
,,,A,!
),,,) .,,
),,,,.,,
?5/,,A,!
2/3. ..
,,,,,.0,
,, ..,,1,...
7,8,“”.
IV!, ,...
21/,2,...
?8,Z ,.”.
7,8
,.(,
),,),,.,,
,,,“,”
,,,.1,
.0,,,,,, ”. DA,. ,0,0.,.,,
.0,,,,,,”. OATA ,400.,,,0
..,1 ,..
.0 !,,,,,
”...,.
,m,. !,m.” ,, ,0,
No Iarge
some
N!(h) profiles
savtig
according
to the values
values
of Te,
Te/Ti,
mean is assigned
the weighted
no sharp discontin”ities
of single
way the effects
constructing
these
number
fixed times;
midpoint
Where
greatest
weight
Vf31.
is followed
it is assumed
could still
in interpretation
profiles
i5(a)
There
interval
frequency
as actually
Hill
conditions
or otherwise
critical
sunrise
the measurements
on the nearest
are not sufficient
mentioned
been joined
at tbe
the Swctrum
was the same,
date at that hour.
to cause serious
It
inac-
determinations.
previously
(see Sec. VII).
to construct
by straight
meaningful
~her
average
15(a) through (j),
lines.
The months
instead
The main features
months
profiles.
the values
of these
here.
were
difference
in the density
being approached
under t:;
I!winter
at the maximum
at this time.
and the lowest
spur”
Tbe critical
near noon or a little
At sunrise,
to
at the corresponding
frequency
of high latitude
frequency
before.
hmax rises
almost
hmax decreases
linearly
of the layer
The highest
midday
because
criticti
was 5.0 Mcps in July and AuWst.
rises
In all months,
ionization
rapidly
but this is not pro-
at dawn and usually
bmax is 10west at abOut 2 tO 3
(around 0700 to 0900) and then has a value lying between
As the day advances,
of conditions
missing,
frequency
that the plasma
observed
it difficult
was 7.0 Mcps in November,
is located
a maximum
derived
points.
are representative
of tbe electron-density
for the reasons
summer-winter
observed
hours after
midnight,
it was assumed
of data makes
nounced near sunspot minimum.
reaches
destroyed,
in this procedure
have simply
briefly
is little
curve
MEASUREMENTS
the paucity
sunspot minimum
Millstone
were
through (j) show results
plots are discussed
mean values.
the Te/Ti
to synchronize
has been made to smooth the plots shown in Figs,
for each hourly
of the
with altitude
of the spectra.
of May and June are missing
have gaps where
In
accordtigly.
if the approximate
To do this.
inherent
values
Te/Ti
with the weighted
of the original
operations
In this
the average
of the ratio
there is a difference
that tbe average
be analyzed
ELECTRON-DENSITY
Figures
and compared
instead
and they are plotted
that the errors
No attempt
a newdetermination
would be found, b“t where
curves
plausible.
is given to the points representing
Finally,
on the day for which it was missing,
curacy
because
points
unless they happen to be uppe~ most.
height could be estimated.
is believed
are drawn through the
points are minimized
the electron-density
measurements
This
spurious
was made during the data-taking
hence,
for tbe
For each hour a plot is then Constructed
curves
these smooth Te and Ti curves
of each hour,
mean is obtained
for each given delay.
would be physically
tbe two temperature
No effort
for Te and Ti
of these temperatures
curves,
good agreement
OF
spectrum.
in either
of determinations,
is obtained from
Us”ally
one, two,
in the corresponding
in each month,
and depend-
for in the compu-
Ti and Te/TC
to bring the mean val”es
height.
and smooth
time of day,
This is accounted
of Te,
Thus a weighted
in each hour,
mean equivalent
of height,
with altitude,
the values
b“t does serve
as a function
a mean of the unco~rected
curve obtained for th&t month,
wms present,
from the best spectra,
and Ti oLtained
of Te and Ti as a function
Te/Ti
were encountered
by taktig
that could be placed
arbitrary,
obtained
Te/Ti
markedly
by weighting
to the confidence
is somewhat
closer
largest
varied
or not any radio interference
This weighting
from
results
of the mean temperatures
three times
of the ratio
time was achieved
this using the mem
of the spectrum
ing o“ whether
behavior
in reduction
and correcting
The q“ality
tations
in the height
changes
of dat% hence,
220 and 230 km.
to about 3i0 km which it reaches
a little
after
rapidly.
t5
.. _______
In summer
the major
and the equtioctial
part of the day.
until sunset,
Du?ing the evening
during the early
(e.g.,
morning
November)
there
A prominent
increase
In summer
the shape of the layer
is nO time when the laYer
of the variation
at sunset.
(March
ning increase
is absent in winter.
of the results
for July and Au@st.
before
the evening
increase
somewhat
delayed
Up
hmax.
at
large
The reason
Similar
behavior
during eclipses
At 650-km
and the magnetic
to great heights
temperature,
its peak.
an e“ening
to maintain
diffusion
before
diffusion.
declination
and January).
There
ionization,
from
inspection
2 to 3 hours
takes place
downward
perhaps
produced
H to decrease
on the effect
rapidly.
Of foF2
condition
heights,
is most impor-
can travel
upward
for tbe exospheric
electron
evening
less
reported
drifts
increase
in foF2 will be
can be attributed
ionization
the effect
to the more
is available
above hmax
is less pronounced
This change between
in the temperature
to
difference
but
sunspot
Te - Ti,
of the higher electron density .66 Tbe
67, 68 if real
~“~t now be
by Eyfrig,
which either
oppose
or assist
the downward
change.
at night during winter
all begin between
for an increase
the possibility
by cosmic
(to be discussed)
to high “alues
until midnight.
to reduction
as a consequence
a pronounced
during these periods,
time heat source
at lower
and piles
at this time is thought to. be the
fast photoelectrons
At sunspot maximum,
increases
evidence
We can exclude
tbe case we should expect
decreases
moves
height
in winter
Also,
in foF2 are observed
These
is some
Sunrise.
of the effect
for elect rod~amic
increases
rise
of foF2 almost
induced by the temperature
sunrise.
in density
that this latter
of the midlatitude
can be attributed
as evidence
Systematic
cember
evident
Tbe eve-
(which depends upon the dip angle 1 according
fall in Te at sunset.
at sunspot maximum
of the magnetic
We suggest
diffusion
high values
and maximum
interpreted
is very
begins to decrease
ionization
scale
by as much as
to about 6 hours.
decrease
Evidently
When I is large,
The absence
extensive
in downward
thought to occur
effect
increase
density
A similar
and thus give
the downward
in some detail.
does serve
may be separated
motion of ionization
(1 > 60”).
increase.
during the daytime,
and less
minimum
In winter
during the eclipse of 20 July i963 (Ref. 47). Increases
65
to depend upon the eclipse being total at F i region
dip being large
A3so,
to participate
maxima
which causes the equilibrium
sinz 1) can be rapid at sunset.
48
In a separate paper,
the appearance
gradual
constant
have been shown
tant for observing
discussed
roughly
its value at any other time of the day.
this is reduced
altitude,
after that at 650 km.
was observed
but remains
in height
shape is nOt changing.
and October)
for the downward
fall in Te at sunset,
changes,
Cause of the evening
reaches
constant throughout
can be seen to be disappearing.
Often foF2 will then exceed
but in the equinoxes
is rougtiy
as a whole to increase
of foF2 on the east coast of the United States is a large
months (e. g., July) the noon and evening
10 hours,
heights,
the layer
hours – when the whole layer
feature
occurring
months, the shape of the layer
The rise in hmax causes
midnight
that this is a consequence
rays precipitating
at 0400 – again
of freshly
into the atmosphere.
in Te at this time.
and this can be explained
De-
and 0200, well befOre 10C~l
in foF2 in March beginning
increase
to maintain
months (November,
as a result
the same temperature
created
If this were
As we shall see,
Te usually
of the inability
of the night-
in the presence
of additional
ionization.
It also seems
unlikely
crease,
On the basis
increase
occurs
that this phenomenon
of such a model,
in the early
is identical
in nature to tbe summer
it would be exceedingly
hours of the morning,
and why large
difficult
to explain
decreases
evening
in-
why the
in Te and Ti which
could give
rise to such an effect
to a large
change in the shape of the layer,
more
electrons
appear
are not seen.
at the peak,
Nor can the increaee
b foF2 be attributed
which causes a redistribution
The increase
observed
of ionization
at the peak is evident
simply
in which
at other levels
above and below hmax.
The regular
months,
evening
decrease
and the density
500-km
region
in density
at all levels
and at about 0400 at hmax.
This suggests
which must commence
near 2.300 and persist
common
at midlatit”de
i“ winter
discussed
minimum.
evening
We suggest
increase
400 km the electron
giving
rise
conductivity
of the electrons.
hemisphere.
in winter,
winter
evening
hours,
a large
line may decrease
hemisphere
time.
by Faraday
are probably
of the
line where the sun
at some later
can be determined
ratio
as a result
foot of the field
hemisphere
to invoke
69 ~
that above about
constant
in foF2 in the summer
measurements
the daytime
by Rothwell,
We suppose
along the whole field
in the wtiter
70
elsewhere.
of the late
Without needtig
as proposed
During the northern
at sunspot
consequence
line is approximately
ticrease
great
The phenOmenOn is
in summer
is a
to another
the temperature
from
It so happens that the evening
stations
increase
from the southern
moon-reflection
hOura.
can be offered.
content of the ionosphere
The two-frequency
same
to a prOnOLtnced increase
ti more detafl
The total electron
latitudes
winter
one hemisphere
must be warmed
smaller
fOT several
(southern)
along a field
immediately
has been discussed
temperate
from
When the sun does set,
and to a considerably
ments.
in the summer
temperature
almost
morning
(though highly speculative)
of the exosphere
has not set.
at these
2300 in these winter
an influx of ionization
at sunspot minimum.
pronounced
that the early
of ionization
explanation
high thermal
is most
that occurs
actual transport
plausible
region
stations
above
near
peaks at about 0230 in the 400- to
reaching
heights,
increase
to be arrested
appears
then increases
This idea
rotation
measure-
most accurate. 7i
na/nb Of tbe number n= Of electrOns
At
abO~e
to the number below nb is approximately
2.5 to 4, and at sunspot minimum the summer
72
We are not in a position to test these values as the profiles
do
day ratio is about twice this.
b~axF2
not etiend
to either
sufficiently
although foF2 decreases
from
winter
summer
~.
to summer.
than winter,
low or sufficiently
from winter
high altitudes.
to summer,
Thus the scale
the density
height
H of the ionization
and this causes the increase
ION-TEMPERATURE
However,
it is clear
that,
at a height of say 600 km increases
above hm=x F2 is larger
in
in the ratiO na/nb.
MEASUREMENTS
I
Plots
plotting
joined
were
with straight
lines.
presentation
smooth temperature
Fluctuations
can be obtained
These
of the lines in these plots.
It was frequently
it is likely
are possibly
be accepted
difficult
the main features
too large
as a result
occur
curves
for each hourly
occurred;
these points were
in these plots as a result
by drawing
smoothed
to what etient
smooth curves
curves
have been lost in this process.
of the diurnal
behavior.
of the influence
The values
on the spectra
and
then
of experimental
to follow
plots are shown in Figs.
the original
interval
the general
errors,
be-
16(a) through (1).
should be smoothed,
Nevertheless,
for heights
and
the smoothed
above 500 km
of He+ ions,
and as such must
in Ti at dawn,
and sOmewhat
with caution.
The principal
rapid
to decide
that some real variations
plots do retain
less
by drawing
as points the height at which a given temperature
and a better
havior
constructed
features
decrease
of these plots are the rapid increase
at sunset.
These
changes
occurred
at all heights
above
about 250 km.
17
—
–.-.—-
I
During
the daytime
250 to 500 h,
the ion temperatures
irrespective
daytime,
suggesting
At night,
Ti increases
There
X.
Seasonal
by about i “/b
months),
were
variations
i7(a)
is converging
of Ti will be discussed
rise,
like Ty
the electron
and then becomes
Despite
duringtbe
daytime
example
ratio
density.
of the ratio
Te/Ti
sequently
decreases
of Te/Ti
increases
that these values
the presence
very
tend to vary
plots
It is at once evident
for the electron
during the major
The influence
above
sun-
part of the day.
Un-
up to shout 400km
of neglected
He+ ions will
to be the quantity least in
500km appears
for the most part;
i.e.,
isothermal
little
suggests
He+ is present
of Te/Ti
density
behavior
altitude
Thehighest
shortly
before
In most months these maxima
isothermal
are correct
months,
v=lue Of the
noon.
Often there
have a value of 2.2 or
During the daytime,
are no violent
with altitude because
of He+ ions (particularly
in the winter
RATIO
18(a) through(l).
was 3.0 in March.
nearly
poor be-
of real fluctua-
is low during these
TEMPERATURE
hence, there
usually
A clear
by only a small heat flux.
at about 350- to 400-w
initially
were
and also because
the nighttime
tbe electron
considerably
at this altitude
of this,
to construct
because
during some of the months,
months the spectra
as a result
are shown in Figs.
as Te becomes
altitude,
Although
These
Te shows a rapid in-
with height (- Z”/km)
In winter
Partly
about noon or later.
ratio
believed
as tidicating
temperature.
is some tendency
to have taken place
can be raised
under observation%
The ratio
heattig.
interpreted
Precisely
encountered
2,4, and the highest
at all altitudes
at that
value at about 2 to 3 hours after
thus Te is likely
OF ELECTRON-TO-ION
is a second maximum
sunset,
Te/Ti,
it has been difficult
temperature
is usually
rapidly
in the daytime.
in Te appear
February).
MEASUREMENTS
Plots
increases
isothermal
is that at 0200 to 0300 in March.
tions in Te with time,
=.
in density
at these altitudes.
cause of the low electron
the electron
There
its highest
we feel the fact that the region
increases
months (e. g.,
temperature.
(Sec. =1).
in Te at this altitude
have been properly
Nighttime
with increases
of the electron
at sunset.
Ti but underestimate
this,
that the spectra
in the
of Ti during the hours of darkess
Like the ion temperature,
to reach
changes
temperature
be to overestimate
error.
rapid decrease
almost
than 2“/ti
the electron
as those for the ion temperature.
(at say 300-km altitude)
are no large
by more
MEASUREMENTS
in the same manner
at dawn and less
but there
later
through (1) show determtiations
constructed
crease
toward
h the height range
up to about 500 km, and usually by less above this height
that Te > Ti at all heights most of the time.
temperature
Ti increases
500 h,
and these appear to be associated
ELECTRON-TEMPERATURE
Figures
of about 2- /ti
in some of the plots for sudden decreases
the winter
time.
Above
that the ion temperature
is evidence
(during
of season.
show an increase
changes
Te is rising
and Ti begins
to *20 percent
Te/Ti
in the ratio
faster
a<.6
with altitude.
than Tr, but sub-
to increase
rapidly.
up to about 500 km.
at night) may cause the spectra
Abo”e
It is
this
to be interpreted
too low a value of Te/Ti.
there
rarely
is a clear
is thermal
during the night,
Instances
June (nea~ozoo),
increase
in Te/Ti
equilibrium
their
ratio
at sunrise
completely
Te/Ti
ofsuch
heating are evident
in October
(near midnight),
and a corresponding
.established
often provides
in March
(near
and in January
18
at night.
a clearer
0300),
decrease
Because
indication
in May (near
i964 (near 2iOO).
at
Ti and Te
of nighttime
0300),
in
Even at times
other than near these definite
e“er
A mo~e typical
particularly
during tbe winter
night,
The possibility
of very
been ,ai~ed by ~algarno62
to believe
effect
associated
implies
large
electron
AVERAGE
but the marked
make it difficult
oiTe/Ti
occurring
months is Te/Ti
fluctuations
to construct
at sunrise
does occur,
morning
it might be expected
of Te/Tiat
meaningful
at certain
of this during May must be discounted,
heating during tbe early
density
that the local heating
only during the summer
would be i.6,
months,
Evidence
with sunrise
increases,
ratio
values
there was appreciable
when the predawn
Xfl.
nighttime
as low as i.2,
plots.
heights has
as there
is reason
hours in this month.
chiefly
in the winter
If an
months
is lowest,
yet it does not seem to have been obser”ed.
This
62
does not hold in the ionosphere.
invoked by Dalgarno
assumption
DAYTIME-TEMPERATURE
I
BEHAVIOR
1
In most months,
part of the day,
fairly
stable temperature
Accordingly,
a period
files
were
constructed
in general,
dependence,
though some
Seasonal
variations
and 500km extracted
from
for these periods.
the behavior
appeared
These
profiles
changes
Figs.
shout 960” K in midwinter
tion is about the same,
of the
and mean temperature
are shown in Figs.
pro-
i9(a) through
marked
(1)
seasonal
can be observed.
i9(a)
wbere
the monthly mean values
through (1) are plotted.
at 300 km.
At 400km the varia-
1020” to 1<60” K, but the winter-to-summer
probably
to the neutral temperature
Tn. However,
satellite results tidicate that Tn is a
73
and not in the summer as found for Ti.
It is possible that some of
the present
of the points in Fig. 20 is significant,
time.
The possibility
mer measurements
netic character
Ap is plotted
also shown is the monthly
part of the variation
whether
mean.
is simplya
in Sec. XIV.
as characterized
by the sun’s radio
1963, so that the summer
ultraviolet.
distance
Also,
increase
no way of testing
seasonal
one,
are any changes
it can be seen
radiation
from
at iO.7cm
this at
of the sum-
days has been investigated.
is no correlation
This probably
for Ap.
and a more
signifies
careful
during disturbed
Fig.
2.0 that
(S io.7)
in Ti cannot be ascribed
It would seem that this is simply
‘rhe mag-
the
were
between
test needs to be
conditions.
solar
the
that the largest
Such a
ultraviolet
flux
was rOughly constant thrOugho”t
to changes
a consequence
in the intensity
of the reduced
solar
of the
zenith
in summer.
The seasonal
altitude.
disturbed
seems
in Ti is a consequence
It can be seen that there
or not there
test is described
increase
in Fig. 21 for all the days on which measurements
and the mean values
in Fig.20
made to determine
hut there
that the summer
being made on magnetically
fi~re
mean monthly temperatures
solar
of Ti obtained here are
in the equinoxes
the fluctuation
made;
the values
at 500km
— approximately
close
At 300-km altitude,
variation
is much larger
maximum
240” K.
for 300, 400
It can be seen that Ti increases
to abOut 1050” K in midsummer
from
I.e.,
the major
during the middle
to change least,
of Te and Ti with height does not have any very
in Ti are shown in Fig.20
from
seem to exist throughout
of 6 or 7 hours was selected
day in each month when the temperatures
where,
conditions
dependence
The scatter
ing interpretation
in the electron
temperature
of the points for the electron
more
difficult.
It is clear,
temperature
however,
months and at a maximum
in the late spring to early
second smaller
in the late summer.
maximum
is -500”
to 600”.
it seems
clear
The variation
which gives
summer.
value of Te/Ti
rise
is larger
than that for Ti,
that Te is at a minimum
The difference
of the maximum
that it is this variation
is shown in Fig. 22 for 300- znd 500-km
It is probable
between
that there
maximum
mak-
in the winter
is a
a“d minimum
is also shown in Fig. 22, and
to the two maxima
in Te.
————
!
The seasonal
distance
variation
provided
for the variation
mer,
because
tbe electron
an opposing
effect
exists,
AVEMGE
Daytime
erratic
average
of reducing
behavior.
variability
from
300km,
increases
height,
but may etiihit
seasonal
heating agency
theheat
Nighttime
but in order
Ti,
of Te,
throughout
changes
understanding
we
of the
Considerable
within the month,
are weak.
Despite
this,
and also
some
electrons
lowest
in summer
of Te/Ti
the cur”e
for Ti.
to conclude
(Fig.
21),
that there
at 350-km
atarat.
being observed
The electron
figure
Because
does not change
If any nighttime
change influx,
density
proportional
in July.
it would be
N is highest
to N2)!3
This appears
The ion temperature
shows
that this was the month that was most
temperature
is a beat source
Ap but that the daytime
amounts with
Te/Ti
altitude.
when the electron
toionsproceeds
values
but above this height Ti
altitude.
the year without any significant
would be a minimum
and one is reminded
is also large
whose magnitude
temperatures
in this month,
and it
depends upon the magnetic
are insensitive
to this source,
as solar
is much larger.
TEMPERATURE
EFFECTS
DISTURBED
CONDITIONS
We have been concerned
sonal behavior
in detail.
measured;
It is, however,
Te and Ti are insensitive
observed
we have divided
19),
The average
mean-temperature
WITH
hence,
important
a part in controlling
have seen that Te and Ti apparently
the high values
ASSOCIATED
in this study principally
of the quantities
may have played
(AP>
hours,
on the other hand,
to gain a better
and Te/Ti
peak in September,
clusions
several
have been taken not simply
does not change by very large
Te/Ti
of 350 - to 400-km
disturbed
daytime
over
behavior,
are usually fou”d to be increasing,
a pronounced
amined
is at maximum
averages
the random
magnetically
XV.
However,
in summer, 74 and
are shown in Figs, 23(a) through (1),
the curve for Te tends to follow
loss from
to be the case –the
“Itra”iolet
and the fast photo-
at the peak.
at night when the signals
a maximum
is active
that Te/Ti
character
peak in the sum-
loss than in the tinter.
of the layer
trends.
month to month reflecting
24 shows tbe variation
is tempting
can also be of-
sbo”ld
and, by taking an average
averages
accuracy
energy
nxonths); hence,
errors
nighttime
by less than in/km.
with height,
Fi~re
(since
explanation
BEHAV1OR
stable
in the wtiter
Ti and Te/Ti
usually
expected
A simple
of the Sun$s zenith
can be discerned.
Below
markedly
fairly
experimental
experimental
regularities
that the thickness
certain
These
exists
the reduced
the peak with less
the change in density
is usually
(particularly
300km.
sight it would seem that Te/Ti
N2GHTTIME-TEMPEWTURE
behavior
as a means
above
for by the variation
is then least at the peak of the F2 layer
namely
have been able to identify
seems
At first
density
this more than offsets
be accounted
that Ti>Tn
in ~e/Ti.
should be able to traverse
perhaps
~11.
can readily
it is assumed
fered
electrons
inTi
increase
with determining
magnetic
We have already
as characterized
undisturbed
at night in Septembe>. –the
most-disturbed
days (Ap<
values
-vs-height
of Apfortbe
dependence
effects
two groups
were
if
concluded
disturbances
that during the
Ap,
Also
we
but this conclusion
rests
on
month.
To test these con-
i4) and most-disturbed
days
and 67, respectively.
The
for the two groups is shown in Figs.
20
daily and sea-
have not been ex-
by the figure
nights,
September
into the quietest
the normal
disturbance
to what extent magnetic
to assess
the results.
to disturbances
MAGNETICALLY
25 and 26.
AS
far as can be determined,
though,
below
etiremely
400 km, Ti was about
large
200-K,
differences
there
and will here
seemed
days (Table
average
little
IV).
closely
The values
electron
small
Apparently
whether
Heating
by several
oftbe
workers.
precipitation
neutral
78-83
constituent
earth satellites,
and Slowey 84 find ATn/AKp
:P index and ATn/Aap
mostly
<5,
gests that either
time,
35 °Kfor
-
= i“K.
Stice
we would expect
at 300 km.
closest
The large
flux from
the sun.
observed
from
source
In either
satellite
remains
case,
results
to be determined,
of height,
significantly.
W.
OF UPPER
SCALE
HEIGHT
Throughout
hibits
almost
by the Kp index).
and ion temperatures.
by electric
by Dessler76),
or aphas
obtatied
satellite
changes.
results
when Kp was
and the values
ultraviolet
conditions
The nature of this heat
that measurements
of T.-1 and T. over a
to the present
determinations
height
hours,
the electron-density
H up to about 500 to 600 km.
distribution
shove hm~- exaTbe value of the scale height
has been obtained from the mean profiles by determining
at what height the electron density
-i
from its value at 350 km. This quantity has a value of the order of iOO to i50 km,
falls by e
and is therefore
values
approximately
equivalent
to the stale
for the mean scale height have been plotted
given for May and June because
for
is absent during the day-
of Tn with magnetic
far superior
with the
for this quantity sug-
of the much larger
phenomenon.
Jacchia
correlation
at times
values
conditions
been reported
which are based on the
is better
nighttime
in the presence
evident
P
F-REGION
most of the daytime
constant scale
were
these
ad
a nighttime
but it seems
T n, should contribute
5, there
with disturbed
made with a time resolution
that during the night in
electron
with K
it may be that the variation
is largely
we should expect
(as tidicated
to show diurnal
results
between
during daytime
upon the
changes — even
agency.
For Kp>
in da flime
(a) the heat flux associated
activity
(as suggested
is inadequate
agreement
etient
of this.
but not in summer.
measurements
correlated
our September
large
and seasonal
in these measurements,
Kp<5.
difference
or (b) it cannot be detected
wide range
by an agency
resolution
as func-
that the temperature
For example,
of increased
waves
is the responsible
The time
drag on artificial
ATi/AKp
rotation
The
IV) and
data to be certain
depend to a very
both diurnal
with magnetic
conditions.
increases
of the results
at night in winter
is the result
in Te on disturbed
- i909 (Table
insufficient
of the heat flux.
heating byhydromagnetic
or by particle
observed
height increases
this scale height increase
It is not clear
ATi/AKp
to etiibit
and Taylor
scale
however,
(iOOO to 4500)
during disturbed
from the scatter
as a measure
period
IV are the temperature
given in T%ble IV presumably
index to employ
the F2 region
fields77
It seemed
heat fluxes to raise Te considerably
71
observed from Faraday
Evans
winter
of the Kp index,
given in Table
and hence would be expected
if K_ is a proper
At night,
but a decrease
at all heights
to Ap than K , though there were
of ATe/AKp
density,
Also
index ap.
related
day.
For the daytime
change in Ti at any height,
as large.
tions of the three-hour
the results.
Ti and Te increased
in Ti per unit increase
was twice
was more
only summarize
sipificant
on the disturbed
days in the daytime
Above 350km, Te is raised over 8006K and Ti by about
75
the behavior of the temperature
on individual days in
elsewhere
At night,
increase
ATe/AKp,
100” higher
appear.
We have discussed
this month,
quit:
Te is the same on both the quiet and disturbed
no electron-density
height at 400- to 425-km
in Figs. 27(a) through (j).
profiles
were
obtatied
altitude.
No values
The
are
in these months.
of
TABLE IV
FRACTIONAL
INCREASES
IN
TEMPERATURE
AT VARIOUS
HEIGHTS
Daytime
Index
300 km
1.4
ATi/AA
400 km
500 km
0.7
600 km
Meon of
All Heighk
-4.5
-2. I
-1.1
-5. I
-2.3
–2.2
P
ATi/Ao
1.1
P
-0.2
-3
-31
-11
-24.8
-21.7
–19.1
-20.2
-22.0
-19.6
-19.8
-18.5
-76
-80
–81
20
10
AT= /AAp
-15.2
ATe/Ao
–12.5
ATi/AK
P
P
AT= /AK
-46
-123
P
Nighttime
ATi/AA
P
ATi/Aa
9.5
7.6
6.4
7. a
23. I
20.9
20.0
21.3
P
ATi/AKp
195
ATe/AA
186
I 85
15.2
16.3
13.2
14.9
43.6
43.1
45.6
44. I
P
ATe/Aa
P
ATe/AKp
I 89
37a
389
422
367
22
—..-
-—,..
Under
conditions
~f diffusive
Ti are changing with height,
i
H
in which
earthrs
hy taktig
+ h), where
true height
below
the computed
arises
there
ones,
as a consequence
Howe~er,
more
the agreement
likely
the TR
explanation
was severe
of the F-region
(5)
h is the true ~titude
h and geopotential
-2
at 400 km).
and assuming
that 0+ is the prticipal
ad
altitude
Re the
z cm he allowed
ion (mi= 2.65 X 10-23 gin),
scale height at 400 km for the average
is a tendency,
particularly
In several
however,
in the early
temperatures,
and these
months (e. g., November)
for the daytime
part of the year.
observed
the agree-
values to lie
It is possible
that this
of the fact that the mean ion mass is less than that of atomic
oxygen.
in October
and a
and November
suggests
that this is not the case,
is that in some months the density
problem
recovery
problem
,
4T+Te)
Ti:T,
—dz(i
[z = hRe/(Re
between
the expected
excellent;”
Te and
in
are also shown in Figs. 27(a) through (j).
ment seems
and ion temperatures
the value. for g (868 cm sec
the shove expression
we have computed
values
altitude
The difference
for approximately
Ustig
H is given
when the electron
=~(logN)=–&–
z is geopotentid
radius].
equilibrium,
discussed
previously
(See. VI-A).
during some days in July.
is in diffusive
equilibrium
profiles
are in error
In particular,
It would seem,
of
it is known that this
therefore,
and that 0+ is tbe principal
as a result
that the upper part
ion up to about 500 km
both by day and by night.
This is an important
observed
in the summer
a lowering
drift
to explain
cannot exclude
HEAT
scale
height.
It seems
though,
that the evening
of cooling
provided
increase
in foF2
of the ionosphere,
quite unnecessary
on the basis
of such drift motions
to invoke
of the results
causing
elect rod flamic
presented
here,
one
they are small.
Q350
A second quantity efiracted
heat flux Q defined
for instance,
a consequence
thie phenomenon
the possibility
FLUX
it implies,
months is simply
of the equilibrium
motions
NI.
result;
from
tbe data and presented
in Figs.
28(a) through (j) is the
in
2 x f06QTe3/2
Te–
(6)
Ti=
N2
where
This
Q is the energy
expression
input required
where
T
Tti
to maintain
a given temperature
gas is cooled
and N are hewn
entirely
determined
chiefly
by the variation
about half that for the electron
a peak where
ftied
reaches
almost
linearly
near sunset.
Q as a function
of N2 in Eq. (6).
density.
a m=imum
throughout
Te – Ti at an altitude
encounters
That is,
Q decreases
(-350 km).
and nighttime.
Accor8tigly,
for hy the rise
23
(above
Howe~er,
variation
of the whole layer
it has
with a scale height
true,
and Q may show
mOnths,
a peak of the order
Since
of Q is
Q has been computed
~ the summer
300 km)
oxygen ions.
and height.
the altitude
At night this is not necessarily
the day and to reach
This is accounted
with atomic
of time
when Te > Ti at all heights,
height of 350 km both for daytime
hcrease
-i
Te/Ti
difference
by coulomb
we can compute
shown46 that during the day,
b;;n
sec
-3
sec-~),
and N is the electron density.
gas (ev cm
85
by Dalgarno.
~ %.,
and Hanson?3 and specifies the heat
input to the electron
has been derived
the electron
‘
for a
Q3Sois foundto
of 500 to 600 ev cm
throughout
the day,
-3
caustig
the electron
the middle
density
of the day,
as the density
It should be stressed
any cell of the elect~on
the ions,
N at 350 b
at 350 M
that these daytime
gas at 350-ti
A considerably
larger
range
iO
altitude.
at that time,
of Q do not ~epresent
They
represent
measured
the total heat flux into
the heat lost in such a celI to
to other altitudes.
when Te - Ti is larg%
hence,
the greatest
un-
in values obtained during the summer at night. Despite this, small fluxes in the
-3
-i
50 ev cm
sec
are found at night in all months; there seems to he no significant
to
variation,
are entirely
These
adequate
fluxes
are of the order
to cause pronounced
of one tenth or less of the daytime
effects,
especially
in winter,
fluxes
but
when there
is a large
heating,
but for want
change in N2,
It is possible
of better
that more than one agency
evidence
we presume
During the daytime,
At night,
h~ax,
is usually
in order
contributes
there is a single
the peak in Te/Ti
source
less than 50 b.
of solar
to this nighttime
whose intensity
is correlated
with Kp.
is about 100 to 450 km higher than the peak of the layer
during those months where the Te/Ti
that Te/Ti
absorption
~11.
is greatest
values
months the peak shifts to
lies
seasonal
diurnal
In the wtiter
amount of heat is conducted
The flux Q350 is most accurately
certainty
to increase,
Evidently
the nighttime
plot shows a peak,
heating
must occur
the height difference
in the vicinity
and N can both have peaks near this altitude.
By contrast,
ultraviolet
250 km.
takes place
chiefly
at heights
below
of 30p km
the daytime
DISCUSSION
A.
High Values
The possible
temperature
Johnson”
difference
Tn seems
outlined
Bo”rdeau
for Electron
the physical
The first
electrons
sible
inelastic
produced
collisions
should rapidly
This latter
this is perhaps
to investigate
with the neutral
reduce
Proceeding
photoelectrons,
63
increase
energy
raiees
of the excess
jugate point.
slowed
beasshownin
gas.
energy
the temperature
energy
Important
nitrogen
to a little
speeds
energy.
into vibrational
electron
heating
efficiency
to th;3(~5ygen)
Eq. (6).
uncertain
manner.
,
24
may iose their
lose energy
by
of the ‘D state of atomic
These
At this energy
interaction
effects
level
a faSt
with other electrons.
gas as a whole.
of neutral prticles
gas via coulomb
depends linearly
(of the electron
ions via elastic
rapidly
states.
less than 2ev.
as those with more than about %Oev can escape
Thus,
In view of the many pos -
are the excitation
density
solar
of photo-
steps in the computation.
the electrons
by coulomb
no longer
by the incident
the number
by which the fast electrons
of the electron
thenumher
difference
are produced
of estimating
average
At low levels
is given to tie
temperature
with height in a rather
primarily
(5 to 50ev)
consists
the mechanisms
to thermal
upward in height,
300km)the
gas
Hanson md
and their work has been summ~;ized
by
85
~~,,
and Dalgarno
have dis-
one of the most uncertain
of molecular
the electron
is finally
effect
Te and the neutral
only recently.
Dalgarno,
of Te –Tn
these too are a function of height.
photoelectron
(above
invol~d,
Hanson,
as a function of height and their
reactions,
oxygen and also the excitation
fraction
processes
recently,
of the electrons
quantitatively
with a wide range of energies
it is necessary
energy;
More
step in any calculation
excitation
Next,
the temperature
anew.
Photoelectrons
flux.
between
to have been considered
and Bauer87
cussed the problem
Temperature
At these
encounters.
and a larger
In this region
upon the energy
along the field
gas bytbe
collisions,
decreases
lines to the con-
fast electrons)
heights the electron
and the temperature
of the
appears
to
gas loses
difference
will
Dalgarno,
photoelectrons,
of solar
of energetic
ignore
and assume
bya.bsorption
very
firm
frequency
and neutral
conclusions.
so~.e.experimental
evidenee
difference
In a more
and might be expected
anticipate
in support af this.
resent
was so. nluch greater
electrons
at heights
This
many uncertain
remaining
conductivity
distribution)
seems
that a theoretical
tures
in the ionosphere
theoretical
B.
Ionospheric
The summer
between the
i3
ha”e provided
presented
bere
conductivity
yconductiont
satisfactorily
oother.h eights
Geisler
answer
deduced. by Geialer
goodinview
and Bowhill
60
report,
innuencing
of the behavior
This seems
with the
for- the behavior
of Te a~d
60
Fi~re
29
(e. g., the
the results.
of the electron
to be a demonstration
of the
however,
that many other parameters
can be changed without siqificantly
the correct
and partly
ateuaspot.. min~tium.
isconsideredquite
is so great
understanding
Thus,
(2) .an up-
to lose heat Solely ””bycollisions
in summer
in the theory.
of the
could be neglected.
from belo>v, and
given in Fig. f% with temperature%
is now at hand.
method to provide
et al.,
made to include thermal..condu ction
heat conducted
The agreement
of the electrons
electron-density
therefore
about 750km).
difference
It was asst~med that the.:hermal
at rnidlatitudes
to the model.
quantities
(above
On the other hand, the results
The ions are presumed
of the temperatures
and Bowhi1160 according
but, as the collision
220 km, and Brace,
mode) has been able to account
during the daytime
ihat the thermal
temperature
that the largest
They lose heatpartlyb
with ions.
shows a comparison
above 600 km, and (2) the ions
than that of the ions, that the latter
ward flux of fast photoelectrons.
neutra~ particles.
a constant tempera-
lies between
above 300km are heated by (i)
counters
to maiatain
at low altitudes
350 and bOOti.
60
attack on the problem,
attempts were
electrons
Ti observed
temperature
particles
should occur near
and an upward nux of fast photoelectrons.
in coulomb
considerably
of the atmospheric
temperatures
or by the fast
at any height is determined
63
Hanson
considers tipward transport
height,
thdt
conduction
electrons
they may assume the electron
indicate
the largest
by thermal
to the value ef Q above 300ti)
but
63
Two other points which Hanson
raises are (1) the
this latter prediction.
85
~~.,
and Hanson”
Both Dalgarno,
electron
at
contact with the neutral
falls ,withheighi,
supports
radiation
conductivity
or less independent
will be in good thermal
Da,garno62
of heat either
(which could contribute
have high thermal
ture more
transport
that the heat Q given to<he
ultraviolet
electrons
is unable to reach
electrons
85
~~.,
It
and ion tempera-
of the power
of the
once it is tiown.
Anomalies
evening
increases
in foF2 have been explained
of this )vork. 48 It has
as a result
been Shown to be simplya
consequence of the cooling of the exospheric
electron temperature
at
70
We hate suggested
that the nocturnal increase in foF2 observed in winter is the con-
sunset.
sequence
of the same phenomenon
lacks a theoretical
treatment
to an observer
of the problem
of temperature
one foot is sunlit and the other is in shadow.
lative
at the present
The major
higher
is anomalous.
F-region
latitude
foF2 values
anomaly”
In part,
ins”mmer,
Hence,
hemisphere.
distribution
This latter
alonga
it cannot be regarded
field
proposal
line when
as other than specu-
time.
temperate
midday winter
that “winter
in the winter
ionospheric
than summer,
is an improper
the seasonal
leading
anomaly,
anomaly
“winter
has not been explained.
description
to a scale height
the so-called
anomaly” of
88
has argued
Wright
since it can be shown that summer
can be explained
as a result
of an expansion
H above hmax that is higher
25
behavior
in summer
of the
than in
~~~
winter.
Observations
of moon-reflected
89,71,72
content of the ionosphere.
These
the total eIectron
of Faraday
conten~ is much less
anomalv
plained
presented
as a consequence
(i)
violently
si~als
yield values
show that the anomaly
than in the value for the peak of the layer.
the loss
here Show that the seasonal
of large
eqand
rates
governing
could be realized
seaao~al
the region
Presumably
combination?’
~1.
radar
for
inthe
tatal
Nevertheless,
an
does remain,
The results
either
pronounced
rotation
changes
as suggested
anomaly
the disappearance
ex-
in the ionospheric
temperature
which might
90 or (2) change the rates of reby Appleton,
the reason. for the anomaly
must be sought in seasonal
of electrons
by changing tbe composition
cannot be satisfactorily
at F-region heights.
88, 92-94
changes
These
in
changes
of the atmosphere.
CONCLUSIONS
The operation
of the Millstone
about i500 hours of observation
explained
features
The results
of the behavior
reported
that conditions
herein
that the temperature
mains
to be tested.
source
Also,
disturbed
remains
in September
the result
ofionospheric
determine
value8
A more
the ratio
at heights
remains
clutter
echoes,
of the Arecibo
i295Mcps
Other
at Prhce
Ionospheric
presented
careful
with height.
Ionospheric
radar
employing
in Canada;
Observatory
useful results
thought
that heating associated
with
The nature of the nighttime
whether
the high temperatures
of the nighttime
agent,
It is unlikely
that,
Rico,
Te,
heat
observed
or of yet a
scatter
therefore,
technique
26
shall be conducted
The region
to
below
240km
of the numbers
there no probIem
(This
to use a radar
of
with ground
is also true
operating
at
the E and Fi regions.
exist in several
in England;
Ionospheric
remain
will lead to temperature
this region.
to explore
at Malvern
and the Jicamarca
this work.
here.
technique
Ti and the ratios
even were
(at 20” elevation)
in France;
spectra
in turn,
examine
) We intend,
the incoherent
from
N,
could satisfactorily
at Nancay
in tierto
should emerge
This,
than those presented
In this region,
obliquely
of the backscatter
of the uppermost
of 0+ to He+ ions.
Observatory.
with a beam directed
groups
likely
common.
in the intensity
examination
effectively,
our existing
Albert
it seems
by the development
which are less uncertain
ions all change rapidly
of this work.
It is currently
at sunspot maximum.
In particular,
it is be60, 6b, 70
This prediction
re-
We do not yet kow
of m increase
as a result
of
un-
will be much less.
will be much more
of the numbers
to be explored
are now understood
hitherto
heating.
Many other opportunities
to be explored.
different
Te –Ti
and results
Several
at eunspot minimum.
at sunspot maximum
conditions
to be established.
were
third source
of the F-region
difference
radar has been described,
*963 have been presented.
apply to conditions
should be substantially
lieved
magnetically
Hill ionospheric
throughout
countries:
as well
Radar
e.g,
as the Arecibo
in Peru.
Many
1:
‘t
ACKNOWLEDGMENTS
Theauthor
is deeply
grateful
to the work presented
vided e“co”ragement
herein.
the
observabV
R. Julie”
wrote
B. Aldrich
Pineo,
M.
number ofpeople
G.H.
Loewe”thal,
Pettengill
who contributed
and T. Hagfors pro-
Mrs. V. Mamn
and W. Mason
shapes of the spectra against which the observed shapes
W.A.
Reid and J.H.
the
task of operating
the
computer
J. H. McLrndperformed
hand analysis
V.C.
and advice.
computed the theoretical
could be compared.
toaconsiderable
McNally
the
programs
this port of thedota
of theresulk
radar
required
shared with other members of
equipment.
for analyzing
reduction.
27
Hen~
and
the data,
and
Contributions
were made by the Mrs. M. Andenon,
and Miss D. Tourigny.
J.C.
totheflnal
M. McDo.gal,
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30
.priester(
NOrthHOl!””d
390
fig. 1. Theoretical spectro ofionospheric
backscatter sig"als computed for"ario"s
values of electron-to-ion
temperature
ratio Te/Ti.
Spectra are symmetrical about
,!
,,
center
frequency.
Ithas been assumed thot the moss mi of the ions isthatof
Abscisso is Doppler shift f normal izedbymultiplying
by radio wavelength
term inversely pro~rtio”al
+. veloci~ofso”nd
for ions.
“E,,”.
I
.
.,,0,
”.,.
O+.
A and.
M, XT” RE
T, =20, (
k/2 .io= 10
0, -
:
:
?
~
ox”,.. ,,,,,..,
)
0
0,
100
o
b
.
!
!.0
2..
,,0
4..
,.0
.,0
7.,
Hg. 2. Effect onspectr”m
inwhich
Te/Ti=2.0
as Progressively Iargeram””kof
He+ ion$ are i“froduced into an @/He+
mixture.
Abscissa same as fig. 1, and mi
represents the mass of the heavier .onstit”ent
(Q+).
31
Fig. 3. The70-meter
parabola
st”dies.
Tripod
for ionospheric
tion.
ing
of
Left-hand
off the
receiver
waveguide
picture),
housed
and
employ edat
str”ct”re
tonne.k
right-hand
in lower
Mllstone
supports
turnsti Ie i“nction
w.veg”ide
Hill
feedhorn
Radar Observatory
and
turnstile
to transmitter
co””ectsi””ction
i“nc-
(in b.i ld-
to First stages
hut.
Fig.4.
Acothde-r.y-t.be
displ.y presenting result of integrotionovero
pulse
Ie”gth
was
0.5
bo,e performed i. computer.
In this meos”rement,
and points representing
lowing
averaged
suppression
output power ore at 100-Wec
intervals.
Fol-
Ieft) are first some ground clut+er echoes
Beyond ionospheric echo ore echoes
and second the echo from the ionosphere.
from two satellites thot chanced to traverse the beam during this measurement.
Large
receiver
time
msec
pulse at right
spends to an increase
(extreme
is introduced
into receiver
in system temperature
32
to calibrate
of IOO”K.
scale
and corre-
,2.0”
,452-,502
t9s3
EST
100-,,,. PuLSE
!
I
I
DENSITY
[percent)
Fig.5.
Plot produced by computer ofelectron
density N’(h) vs height.
Com~”ter
draws straight lines be~een
measured points which are at
15-km height intervals;
Fluctuations observed obove500-km
heightare
errors d“e to noise and not true variations
in electron densiw.
Below
200 km, receiver
wassuppressed
against gro.”d
clutter
echoes.
ooor
I ––
“coRRECTED
B. CKSCATTCR
‘0:=
,,s?1.
NORMALIZED
ELECTRON
PROFILE
‘
205070
DENSITY
l,.rCe”tl
fig.6.
Example of combined electron-density
profile obtained from
plots (e.g.,
Fig.5)
for O. 1-, 0.5-and
l. O-msec pulses. These particulor measurements were made at same time as rocket was launched from
Wallops Island, Wrginia.
~fference
beWeen
rocket and bo.kscatter
profile is largely d.e to fact that u has been assumed constant toobta;n this profile.
33
t
i
200
t
t
,
\
20
T,/Tl ELECTRON
TO
2
TEMPERATURE RATI.
ION
Fg.7.
Variation ofelectron-to-ion
temprature
ratio Te/Ti
from spectra meosured during period 0834to
1005 ESTon2J.ly
.
obtained
1963.
2,ULY
(963
,030 ,,,
\
\
\\
\
1
‘.
\
\\
\
,...,,,,,,.
—
N&SA
,Cw
PROF)LE
ROCKET,
ROFILE
..0,. s,..”,)
..,. ROCKET PROFILE
(,.,,,.,.,.3”, .. ..()
I
,
NORMALIZED
I
7
,0
ELECTRON
/
2.
DENSITY
I I I 1 II
5. 70!
1,.,,.”,1
Fg. 8. Backscatterelectron-densiwprofile(Eg.6)oftercorrectingfor
variation of electron cross section o, with height according to Eq. (4)
and resu[k
for Tefli
made at 0922,
b.ckscatter
presented
in fig.
but ground clutter
me.s.rement
until
7.
ROcket measurements
echoes obscured
1030.
34
F-region
were
peak
in
Fig. 9. PION showing variation
as functions of scaled quantities
peak
echo ~wer
of contiurs of constant Te/Ti (= R) and Ti
f a“d x. Ordinate
x is the rotio betieen
in the wing (fig.
is DooDler
shift of a mintof
,,
in absence of eq”ipmental
l) to that at center
frequency,
and f
half oeak intensiti.
ktted
lines show values
effects, whereas S1 id I ines show change i“ x
and f when spectral distortion introduced by transmitter pulses and receiver
filte~ is allowed for.
_~
T, = ION TEMPERATURE
=
RATIO
. 0.
R TEMPERATURE T, /T,
,, –
,0.
,“LSC w,.,.
—
–——
PLASMA
PL&s MA
= I.,.,
FREQ, = 2.5 ..,,
FREO, = 1.0MCP,
.
32 –
,,OO.
/
*
,300. ,50~
.,(
8
?., –
Fig. 10. Two spectwm analysis chotis similar to full lines in Fig. 9 are
here superi reposed to i I Iustmte dependence of spe.twm shapes upon electron density N (specified i“ terms of o plasm. frequency fP).
Density N
enters
because
equations
where XD is Debye
contain
ratio
length (= ~-2).
35
of radar wavelength
A to AAD
——
~
.,,,
0, .0”, v.L”ES OBT.INE3
BETWEFN
0234 AND 1005 EST
VERTIC.L ,.,, DENOTE EXTENT
O“’’LOR’NG’”LsE
,0 .,.
~.
v’Oo’”~\
i
,OOAO
)
“’”’y;
“,
,oO~/.0.
I
i
T,
PJ\
T,
L
o
I
,.0
K,NE,,.
Variation
fig. 11.
Sol id I ines denote
!
!
!000
,500
,EM,ERhT”RE
,000
(~.1
of electron (T,) and ion (Ti) temperatures observed on 2 July 1963.
values deduced on assumption that only 0+ ions are present of al I
heights.
Dotted I ines indicate how temperature
might vav
if percentage of He+ ions
becomes significo.f
above 5~ km and i“cre.ses to value of 20 percent of total at 720 km.
IS –
g
loo~!.
0+
Tr=2,00e,
T,/T,=10
,2
?
8
:
<
0,.-
:
z
807.
O+; 200/.H,+
o 4–
.
2.6,
‘0’2
hg. 12. Mean of al I experimental
profiles obtained at greatest height (720 km) during
period 0834 to 1005 on 2 July I ?63 is here compared with closest fitting precomp. ted
curves for on 0+ gas and mixture containing 80 percent 0+, 20 percent
fit could be obtained by adiusfing theoretical
curves so that for 0+,
Tefli
= 1.14, ..d
for O+/He+,
Ti = 1400° and Te/Ti
I“tions ore experimental Iy indistinguishable.
36
= 1.4°.
He+.
A better
Ti = 2040° and
When this ‘s ‘one,
‘0-
3.,
3.2
L3-3!-&I,aI,))
—
E
(ON = 0. [80-/.) He. (20-/.1
W,OTH = I .s.,
FREO. = !.5Mc, %
r,., ,
f
no
——
,“.s,
PLASMA
,e,
~ = ION TEMPERATuRE
R = ,FMPFR.TURE RATIO T,/T,
!ON=O.
I
,,
Fig. 13.
4.0
Spectrum analysis
1
1
6.0
f (kcpsl
.
7..
I
I
8..
,0
chart for fp = 1.5 Mcps and different
;on compositions.
s01 id I ines represent whol Iy 0+ ions in absence of equipmenta~ ~ffec+$; dOfted lines
denote 80/20. percent mixture of @/H&+
iOnS Ob,erved usin9 o I ‘m$ec Pulse. If “x”
and + are the only
Te/Ti
quantities
scald
from the records,
can. be obtained depending ..pon whether
wi~ly
differing
values
I
‘“:~
(0.
2
5
10’
ELECTRON S/.m3
2
;,
Fig. 14.
Alo.ette
Comparison be~een
electron-density
profi Ie obtained by the
satellite
and backscotter radar on the morning of 12 July.
Large discrepancy in two profi Ies above 500 km is attributed to improper
recovery of receiver TR at this time.
(The Alo.ette
profile was kindly
provided by Dr. T. E. Van Zondt.)
37
of.
Or nOt HE+ iO~$ are ussumed pre$enf.
~
?00
CRITICkL fREOUENtY
if8 19s3
10
1.s
600
—
1,s
20
5W
z
~
2.5
:
..<.0
‘\\ ,N$UFF,CIEMT
3.0
#
400
:
DA1k fon
j.5q“
“FANINtFuL
..~:
.
.2,0
300—
.<..
..hmox
AvERAGis
4.0
4,5
5.0
5.5@
hmox
6.0
.2,0
---.-- ...
20oo!~/2/f
;Op,
fsl
EST
(b)
(.)
-~
~
100
).5
CRITICAL
—
rR[QuENcY
JUL (963
10
800
—
1.0
2.0
1,5
so0
?
:
;:
:
=
:
~
2.5
30
400
35
4.0
5.0
,,,J:-,,
~
4’
\
5.0
‘ma:\
.
2001
040
I
>,,&--.’’’’’”
v
Contours
of
.onst.”t
38
plasma
frequency
0
,,
I
,$
(d)
(.)
15(a-i).
II
E:T
!s1
Bgs.
.,-:: & .
(Mcps).
,0,5
Iu
20
~
~
,,0
20
CRITICAL
FREQUENCY
SE? 1963
‘t
j,
1.5
1,0
\
\
i
\
600
, ‘1
,\
25
\, ~1.s
?
:
E
s
:
~
:
\ ‘\
\l
\\
,,\, 1
3.0
500
:
5.5
p
, ‘,‘\
~ ,\\
~
4.0
DATA POOR
400
\\ !
\\ \
AURORA1 ECHOES
4.5
y,
5.0
5.5
300
*r
r
/
h
_~ #,m!~../-
..>
i~
;3.0
:!
,
,
B,
?004
0481216
481!
2024
EST
(e)
(0
~
!00
CRITICALFuEouEtic7
2.0
1.5
Ocl 1963
‘O\
6W
20
1.0
500--
‘5
z
5
<$
=
‘5\
3.0
I
:
l.,
4W
3.5
OAIAFOR
4.5
MEANIN6FU1
T
~~
5.5 ‘mOx\.
2,5
\
..
.hmo,
~ma,-
\
Zm
2.0
2“\
5.0
Av[RhcE$
,m T
:\,
20\
40
INSUFFICIENT
20
25
jj_
&A,
1620
EST
@
6.0
“6.0
?3,
5.5
5.0
M5
0481216
2024
EST
(9)
Kg.
15.
Continued.
39
~
I
(i)
[s1
(i)
Fg. 15. Continued.
40
80”
:FE’”6
w
_~
\/\ d
~
=
600
Ti MAR1963
500
W\
Soo
1200
1200
I100
\
\
400
2
=
~
~
1!00
1000
\
300
~“:
\\L/
\_/
‘u
900
r
..-4
800
\
-\\___
8QQ
6oJ\
\
\.
too
100
100
0461!16
I
I
I
,oo~
I
I
0481216
2024
20
EST
EST
(a)
(b)
~
Ti
HAT1963
w
100
100
2000
u
1800
~
1100
600
600
!100
1600
lbbQ
1500
?
z
;
5
z
.
m
.
SW
=
&
—
‘g
500
1400
1000
900
1300
900
1200
400
400
~~
y~
[
1100
300
300 ->
0481218
2024
20
EST
(d)
(.)
Rgs. 16(a-1).
100b
0491218
EST
Variations
of Ti with time and height.
?
I
EST
(e)
(h)
(9)
Fig, 16
Continued.
42
i
I
EST
(i)
(i)
~
700
$00
500
F
5
~
E
400
3W
200
0481216
202
[ST
EST
(k)
(I)
fig. 16.
Continued.
43
...
1, FEB198j
500
2600
400
z
~
1200
~
~
\
2200
300
2000
i~
1800
1400
100
~!;
I
2400
1600
I
Is
I
I
,00
0481218
I
20
I
I
\
I
2094
EST
;;1
(a)
z:
:
=
0481216
202
EST
EST
(d)
(.)
Figs. 17(0-1).
Variations
of Te with time and height.
44
I
~
100
100
800
880
SOo
j
F
=
:
~
q 500
~
400
400
300
300
too
04812!6
04812
20:
[ST
!s1
(e)
(0
~ 1993
2900
/
300$
~
~\~
‘
28[
/
/,600
2800
2600
1400
2600
000
up
2400
1200
1800
2200
1000
P
0
48121620
EST
(h)
Fig. 17.
Continued.
45
,:ri
TeOCT198j
700
~
Q
~1‘
2800
,--,
f’,~oo
-.,2400
.
/
?~oo
1400 ‘II
*6Q–,>\\
I 1400
/,,,
\
2oy
1200 \\\,
,,
\\\
[000
\~[J
,-
2600
\
1
\
II
300—-.
3000
\
\
!
\,2800
600
?
~
> $00
v\
/\
/
\
\
180~
1600
?
\
,
\
\
\
~\1200
,
\\
\
0481216
202
?oo&._. ..-+..-....~..
. .....~_._...o_
EST
C$l
(i)
(i)
—
I T, 0EC1983
1,
if
‘i
d
100
/
\
2400
00
?01
2200
1200
A
IQW
.
2000
A
&
2000
1800
Iw
12
1800
Iwo
16
20
EST
(1)
(k)
Fig. 17.
Continued.
~
~
ton
600
Te/Ti MAR 1983
leni FED1983
1.8
L
2.0
1.6
Soo—
y
1.8
2.2
[.8
P
1.8
2.4
400
1.9
3
:
>
#
1,6
2.s
r
o
380
2,2
!
2.0
~$)
—
1.4
2,0
IA
I,6
m
r
100—
200
,.,
,.,
E:T
EST
(.)
(b)
=
100
Te/Tl AP8 196j
\
,,,\
2.0
\
~\2.2
2.0
2.4
2.2
‘h
2.4
0
j
L
200
04
1.2
1.!
&
g
12
EST
1s
20
EST
(d)
(c)
Figs. 18(a-1).
Variations
of ratio Te/Ti
41
with time a“d height.
~
Tell; JUL!963
1,2
100
1.4
‘~
1,8
(.6
600
:
\.&
f
‘
:
~
~ 500
1.8
1,8
~
2.0
2.0
400
2.2
?.2
~@
300
!y
d
,
0481216
2024
EST
EST
(f)
(e)
1.4 ‘
~ 1.2
m
EST
(h)
(9)
Fig. 18.
Continued.
48
I
I
,:,,10,,,983
I
EST
EsT
(i)
(i)
=
1, IT(
Occ 196j
’00 T,/Ii
/;9
,
II
\\
‘oat
n
!.9
90
z
5
:
~
L
2.0
o2.4
2,2
400
2.4
0
300
u
1.8
2.2
2.0
,..
,W
1.8
04U12
EST
EST
(k)
Fig. 18.
Continued.
49
I
DAYTIMEAVERACE
[0900-1400
ESTI
FEBRuARY
196j
1.4
‘
0
600
I
I
I
$400
I
lelli
1
1800
I
I
I
1
I
1000
3.0
26
2.2
,.8
I
I
t2n0
I
I
I
2600
I
30
TEMPERATUREI*K)
(0)
1000
=
DAYTtMEAVERACE
[09001400EST)
MARCH1963
I
t
0
I
Soo
I
I
I
TelTl
I
Iboo
I
I
1400
I
I
18M
3.0
2.6
2.2
1,8
14
I
I
I
!200
I
I
I
I
I
2800
TEMPERATURE[“K)
(b)
figs,
19(a-1).
Average
daytime
behavior
50
of Ti,
Te,
and Te/Ti
with height.
-
...
1
DAYTIMEAVFRACF
(0900-1400
EST]
APRIL196j
800
/)2
\,n
\
Soo
zg
=
3
= 4W
\
\
\\ Ie/Ti
Ti
T,
‘.
;d ❑
❑/
,’
,0
200
!,4
2.2
1.8
3.4
3.0
2.6
I
I
I
I
I
I
Te/Ti
I
I
o
600
I
1000
I
I
1400
,
1800
I
I
I
2200
I
I
2600
I
3000
TEMPERATUREfaK1
(c)
1.4
I
1.8
2.6
2.2
1
I
I
I
I
Te / Ti
I
0
Rw
I
Iw
I
I
1
(4W
Inw
TEMPERATURE
I
22W
(-k]
(d)
Fig. 19.
3.0
I
Continued,
I
I
mo
I
$Ow
n
800
I
I
low
I
I
(4W
I
Te/Ti
I
,800
3.b
I
I
I
I
I
I
2.s
2.2
I.t
1.$
I
I
Z2W
I
I
,8,0
I
3000
TEMPERhIURE[SKI
(e)
OAY1lMfAVERAGE
[0800-1400
EST)
JULY 196j
t
o
600
I
I
low
I
1,/Ti
I
1
I
I
1800
1400
TEMPERATuREIQK)
Kg.
]9.
Continued.
52
3.0
I
I
I
I
I
26
2,2
1.8
1.4
I
I
2200
I
I
9600
I
3000
m
OAYIIHEAVERA6E
[0800-(400
EST]
hucusl196j
+m
\
Te/;\\
71
n
‘.
)
.
,.+.
I
1
0
6M
I
I
I
I
1000
I
,,8
2.2
I
2B
I
I
T,/Ti
I
I
I
I
1400.~~~
18W ~~~
TEMPERATURE
(’t]
I
X.4
3.0
I
I
I
I
22W
I
I
2WQ
I
$000
(9)
(MO
=
❑ ... .
OA?TIUEAVERAGE
(IWO-1500NT)
SEQ11U8ER
1963
~...
800
t:::
t...
I
I
o
600
1.*
I
low
I
I
1.8
I
1400
2.2
I
I
2.8
Te/li
I
I
I
I
?20,
1800
TEMPERATURE(*K)
Rg. 19. Continued.
,
53
3.0
I
I
I
2800
(
!
30
,600
1800
!4W
loan
TCMPfRATUREISKI
a
f
Ti
~Te/Tl
Te
f
\
‘h,.
‘\
.
b,
d
.~ d’
_D.
t.?
1.8
1,4
I
3.0
Z.e
Te I T,
I
o
600
I
1000
I
I
I
I
TEMPERATURE
[’K)
(i)
fig.
19.
Continued.
54
I
2?00
18W
1400
I
I
I
I
I
DAYTIMEAVERACE
[lbQQ-15QQ
EST]
NoVEMBER 196j
I
I
1$00
I
$000
‘:F
1.4
18
1
1000
1
1400
2.?
2.6
I
3,0
I
2200
I
2600
TelTi
0
600
1800
TEMPERklURE
J
[SK)
/,
)1
(k)
DAYTIME
AVERACE
(1000
-1500EST]
JANUARY1964
[I
d.
.,.1, ITI
..
\.n
T[
T
e
‘\
b
/“
--n
D--
1.8
!,+
I
1
0
6W
I
““
I
1000
I
2.2
I
i
Te /‘i
I
TEM?ERATU8E
l,k)
(1)
Fg. 19. Continued.
55
I
I
I
22W
(8W
14m
3.0
2,8
I
I
I
I
I
?6W
I
31
—
I
800
600
$10.1
,
I
JAN I
1964
fin
ukR
A?R
u~~
fig. 20. Seasonal variations
flux
at
10.7
cm
is also
JUN JUL
1963
i“ average
‘UC
daytime
I
I
‘Ep
values
‘CT
of
‘ov ‘Ec
Ti.
Solar
radio
shown.
\
<’
L..
to
0
,:4 \ FIB
fig.
21.
values
of pla”etav
conducted in 1963, together
196j
magnetic
index Ap on days when
observations were
with monthly means of these vol”es.
5b
3500
-
fig.
I
,.
,,
J
22.
Seasonal variations
i. daytime
T= and Te/Ti.
600—
\TelT,
b,
1,
‘
500
?
:
\
:
.
#
400
.k\
.
0°
\
NIGHTTIME
AvERACE
[2100-0300
EST)
FE8RukRY1983
b
300
-
;[J
,.t
-,.4
,//
,,
,8
,,,
1400
,800
l,IT:
200#oo
,200
,000
800
18
TEMPERATuRE
1°K1
(.)
T,
~1T’
,
.
/
.
NIGHTTIME
bVERA6E
[2100
-0300E$11
MARCH1963
.
I
1,[ 1{
2W
GM
[
I
m
I
I
IWO
I
I
12W
I
14W
I
I
,6W
1
I
1800
TEMPERATURE
(*K)
(b)
Figs. 23(a-1).
Average
nighttime
behavior
58
of Ti,
T,,
and Te/Ti
with height.
/T,
L
600—
/
Tel1’
500—
z
5
:
~
400—
NICNTTINE
AqERACE
[2100
-0300ES11
APRIL1963
300—
I
1,/ T,
2W
800
I
I
8W
I
I
lm
I
!?00
I
I
(4W
I
I
(600
L
TiNPERklURE
(*K)
(c)
‘\
)
Te/Ti\
\
0
q
t
\li
\
1,
/
!
Y
t/
NIGHTTIMCAvERAGE
,01
i2100-0300
EST)
2.0
1.8
1,2
L/
I
I
I
JI
T, /Ti
I
ma
800
800
I
I
1000
\
1
1
TEMPERATURE
(“K)
(d)
Fig. 23.
Continued.
59
:
[
1
1400
1200
1
1
1600
I
700
r
~
\
1,
Ti
/1,/1,
I
60$—
~
500 —
I
?
=
I
:
g
400—
NICUITIUE AVERi6E
l?lQO-OjOO EST 1
JuNE 19Sj
30o—
,.0
I
I
1, /li
I
800
I
200
6W
I
1000
I
1
I
,200
lENPfRATURE
I
,400
I
!600
I
I
1880
I,K1
(.)
700
❑
.
~
/
,
/
/
800—
1{
,{e/Ti
/
%00—
z
5
~
g
400—
NltHT1lME
AVERACE
[2{00
-OjOOES1l
JULY196j
300—
2.0
I
I
1,/T!
no
I
8W
I
800
I
I
1000
fig.
I
I
,400
1200
TEMPERATURE
[s[l
23.
Continued.
60
I
I
1600
I
1800
:J,
le/T{
500
?
:
I
1,
Ti
/
:
❑
l”
:
400
.
NIGHTTIME AvERA6f
●
-
[?4QQ-OjOO EST]
1:
300-
AUGUST 1963
.g’
0
1,4
~?
!.6
1,8
2.0
,400
1800
Tel Ti
200~~.
I
~;.
1000
1200
1800
lE#PERkTURE
(<A)
(9)
\,
7\Ti
;)>
Ieli?,
500
~
T.
\
:
~
*
400
\
\
.
\n
0
~
NIGHTTIME
300
•~,
_
----1.2
d’
4VLRAC[
(2200-0200
EST)
SEPTEMBER196j
~
1.4
1.5
1.8
2.0
1400
Im
T,/li
2M
600
8W
1000
1200
TEMPERATURE
(-K)
(h)
k
Fig. 23.
Continued.
18
TEMPERATURE
C9K)
(i)
200
800
I
I
1000
I
I
1400
I
Ja/li
)
,800
TEMPERATURE
ISKI
(i)
Fig.
23.
Continued
62
I
2200
I
I
2600
I
3Q’
600
[
x,
o
Q,
‘\
\:e/Ti
$00
I
~
=
=
=
\
Ti
Te
‘\
ko
400
;,
;
/’
,6’
300
H16MTTINF
AVERA6E
(2200
-OjbOFST)
DECEMBER19$5
.
.
.
1,4
H“
1;
fiz
28
10
Telli
200
600
,000
!400
1800
2200
2600
TEMPERATuRE
(SK)
(k)
100
=
t
(1)
fig.
23.
Co”tin.ed,
b3
30(
fig.
24.
Seamnal
variations
in nighttime
b4
Ti,
Te,
and Te/Ti
at 350 km.
,000
~
SFPTEMBERAVCRAG[
[1000
-1500[S11
DhY1lME
800—
1$,
/
,, /
/
/
800
z
:
I
/
//
/
:
g
/
/
/
Uo
/
/
/’
;)J
200
/“’
/
—MACNETICA1lV
QUIET
Mh6NE11CALLY
DISTURBED
————
o
600
1000
,800
1400
2200
Xoo
300
T[H?ERATURE
[,[1
Fig. 25.
Comparison of overage height dependence
of Te .“d Ti o“ magneti..lly
q.iet days (Ap< ,4) a.ddisturbed days (Ap & 19) in September.
there ore “o maior differences,
As can be seen,
m
—
600
u’
500
T,
z
:
~
~
:
\
SEPTEMBERAVERAGE
[2200
-0300EST)
HIGHITIMC
T, \,,
,,1
\
/
\
400
)
,~
,~’
,~’
300
_-—
/
——
,,
/
————
I
‘oo~.
800
,000
(200
TEMPERATURE
1400
MAGNETICALLY
QUIET
MAGNETICALLY
01STUR8[0
1600
800
[,[1
Fig. 26. Comparison of average height dependence of Te and Ti on magnetically
quiet nights (Ap< l!) a“d disturbed nights (Ap > 19) in September. At night,
large increases .ss..,oted with disturbed conditions occur in Te and Ti.
1“
,:.
I
I
I
I
I
0481216
I
I
>OP4848
I
I
20
I
I
:
12’6
EST
EST
(b)
(.)
20
I
I
I
048121$
I
1
20Z6
I
1
I
I
I
04B[P16
I
pa?
EST
E6T
(d)
(c)
at 400-km
figs. 27(.-i). Comp~ri~on of observed scale height of electron-densi~+d~tribution
with that .omp” ted from measured values of Te and Ti, assuming any O
,ons are present.
bb
al tit.de
OUSERVEQ
I
I
[
0481?1s
I
,-
I
?0
EST
EST
(e)
EST
(h)
(9)
Fig. 27.
Continued.
67
200
~
OEC1963
I
0
I
(i)
QBSiRVED’
40
I
I
I
I
0481~16
I
I
to
!s1
200
JAN 1964
Kg. 27. Continued,
=
’000
FEB 196j
~
200
800 –
–
!s0
_‘0
:
TE
an –
“
/
J
<
h
~
/
o
400
z’
~
200
,,,
,,,,”
,,,’
.,”
o
\
4
I
8
I
12
16
20
28°
EST
EST
(.)
(b)
ESI
EST
I
(d)
(c)
figs.
28(a-i).
Heat flux Q350
required
to maintain
temperot.re
69
difference
Te – Ti observed of 350 km.
’000
AUG 1963 *
’000 sE? 196j
_,:
/
.
?= 600–
/
“
fll
~
~i/
~
k 400
-i
:
200
Q
350
200–
200
-..1..
048121620
L
04
24°
EST
EST
(e)
(9
1000
1000
~
OCT19Ej
200
– !60
+ “i
_-
/q’ho4’p
‘u
NOV1963
m
200
9
/’\~
800–
/
?: 60@–p. /
“
/b
~
g
H
800
gQ.
4,
_-
Q .W,
/
‘o
$
+
120_
&
TE
~
g
&
o
350
s
ti 400
:
.
,,,,
~d’
?,
600 -~wo?,
“
s
<
80
j
,,5.,
400 —
:
.
40
200
;,~;
,,,
,.,’
4
8
200 –
“%
,,“
0
~
12
16
20
048121620
24°
24
EST
EST
(h)
(9)
Fig.28. Continued.
70
““~z”
EST
fsT
(i)
(i)
Fig. 28.
I
t
I
,000
Co”ti””ed.
I
2000
I
I
3000
I
TEMPERATURE
{SK)
Fig. 29. Comparison of temperature distribution with height shown in Fig. 11,
with theoretical
calculations
by Geisler and Bowhi 1160 for midday in summer
at s.ns~t
,1
13-31-8836-11200
’000JAN1964
minimum.
SIFI ED
-. -....,
. .. . . ... . . . . ..
DOCUMENT
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body of mbefz.ctmd tnd.xlndm“ofatlonmust be a“faradwhen theoverallreportia classified)
*., REPORT SECURITY CLASSIFICATION
&c Tlv,,, (cow.,.,. a“th.r)
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..11.”
Unclassified
Lincoln Laborato~,
M. 1.T.
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None
REPORT
T,TLE
Ionospheric Ba&scatter
.,, c,,,7, v, ..,.,
Observations at Millstone Hill
(T,P* of caporlandi“elu.ive .at~.>
Technical Repom
.“,.O,
(s,
(Lea<
name,
firs,
rime,
:n:tt al)
Evans , John V.
REPORT
7.. TOTAL
DATE
NO. OF PAGES
22 January 1965
,..
C0N7R&CT OR ~.AM7 .0.
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O, EC,
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GIN ATo
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REPORT
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Technical Report 374
19(628)-500
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NOTICES
12. SPONSORING
NOTES
MILITARY
Air Force
None
AcTIVITY
Systems
Command,
USAF
A,5T, A.,
Studies of theelectron-densi fy, electron andiontemperatures
in the F-region were made bymeansofgoundA70-meter parabolic antema directed
based radar observations at tie Millstone Hill Radar Observatory.
vertically
and a 2.5-Mw pulse radar operating at 440 Mcps were employed for these measurements.
Results ofobservations extending over aperiod ofone year from February 1963 to January 1964 arepresented. The ratio Te fTi achieved a maximum value ‘2. o tO 2.6 at a height Of ~Out 300 km sOOnafter dawn,
irrespective of the season. There was little chmge in height dependence in this ratio throughout fhe daylight
hours, and at sunset the ratio feUwith atimeconstmt
of tie order Of an hour. Atnight Te/Tiwas Occasionally close to unity, but more offen a sipificant difference remained in tbe temperatures at all heights.
Iontemperature increased witb height at all times, but above 500km this may beduein part totbe presence
of mutinom
amount of He+ ions, which consider&ly affects the interpretation of the si~al spectra. E1ectron temperamres were largely independent of height hove abut 300 km. Evidence is presented of ionospheric heating during ma~etically disturbed conditions, but it is show tiat this is only of great importance
at night.
.Ey
wOROS
ionospheric scatter
Millstone Radar
F-region
electron density
temperature effects
heating
sisal-to-noise
ratio
parametric amplifiers
spectrum analyzers
TR tubes
72
—
~,
Security Classification