P
Unclassified
MASSACHUSETTS INSTITUTE OF TECHNOLOGY
LINCOLN LABORATORY
STUDIES OF THE F-REGION
BY THE INCOHERENT BACKSCATTER METHOD
J. V. EVANS
Group 314
TECHNICAL REPORT NO. 274
24 JULY 1962
MASSACHUSETi
LEXINGTON
Unclassified
/
ABSTRACT
The Millstone
Hill
radar
facility
operated
has made measurements
of the distribution
ionosphere by observing
the weak incoherent
urement
were first made early
on a routine
in 1960
by M. 1. T.
of electrons
backscatter
and were
basis at least once a week.
the basis of the resul k obtained
scale
height of the electron
perature
is not very dependent
urnal variation,
hours of darkness,
around
nmn
increases with
on height,
to the expected
value
of special
1961
analyses
of ele. -
study.
are:
ratio
it increases too
On
(a) the
(b) the ion tem-
though it does show a marked
cross section
when al Iowo”ce
reached
height,
temperature
but during the daytime
and (d) the scattering
These meas-
The distribution
has been a s“biect
(c) the election-to-ion
of the
thro”gho”t
Res.1 ts of spectral
to dote the conclusions
density
signal.
conti””ed
in 1962 are also given,
trons ~bove the peak of the F-region
Laboratory
This report presents al I the electron
density profll es measured up to the end of 1961.
of the signals made early
Lincoln
in the. F-region
is I:1 during
peak value
for the electrms
dithe
-1.6:1
is close
is made for (c).
ii
-
TABLE
OF CONTENTS
ii
Abstract
I.
11. ELECTRON
111.
IV.
V.
i
1
INTRODUCTION
DENSITY
A.
Methods
B,
The Observations
C,
Accuracy
D.
Discussion
PROFILE
of Observation
3
MEASUREMENTS
3
and Data Reduction
7
22
of the ResultS
25
of the Results
25
4.
General
2.
The Height of Maximum
3.
Scale Height Hi above hmax
2b
4.
The Total
33
SPECTRUM
Considerations
Electron
Electron
Density
26
hmax
Content of the Ionosphere
34
MEASUREMENTS
34
A.
Introduction
B.
The New Spectrum
C.
Results
D,
Temperature
E.
Summaryofthe
of Observations
ABSOLUTE
35
Analyzer
36
int962
39
ValUeS
Spectrum
SCATTERING
43
Measurements
CROSS
SECTION
OF
THE
ELECTRONS
43
43
A.
Introduction
B.
The Radar Equation
for an Extended
C.
Approximate
Equation
D,
Values
E.
An Average
F.
Summary
Radar
ofv A,
qr and v~for
fora
44
Target
Millstone
Millstone
-Type
Radar
Antenna
47
49
5i
Value for um
54
54
cONCLUSION
111
I
STUDIES
BY THE
INCOHERENT
The scattering
recently
of X-rays
has practical
postulated
section
by electrotls
the free
radar bean, were
electrons
there
ae=(~)2
correspond
to power
conclusion
of independent
electron
reflected
oscillators.
the echo power
the echo power
targets.
Alternatively,
of irre~larities
trum
one can arrive
it would be difficult
The first
in detecting
employed
of iookcps
Thus,
Hence the radar
the phases
cross
of the N
power
work of Lord
changes
In this case the reflection
section
proportional
sec -
of the
waves
to N Ve.
on the behavior
by considering
of the dielectric
Again
the
constant
can be considered
index of the medium.
density
energy
the cross
reflected
Rayleigh2
at the same result
instantaneous
to the electron
to arise
it is found3 that
N.
would completely
fill the beam of the radar,
4
as for conventional,
i.e., “point”
R only as i/R2, not i/R
that the echo power
for a wavelength
since the echo power
of 4.5m)
would exhibit
because
would be distributed
a Doppler-broadened
spec-
of the random thermal
motions
over
a wide range Of frequencies,
to detect.
success fulexperimental
the echoes
a transmitter
observations
by use of a radar
operating
came later
of a linear
important
that,
array
contrary
covering
in i958 whe” Bowles4
at a f?equency
with a peak pulse output of about iMw,
which took the form
discovery
to normalize
the electrons
with range
he speculated
as that which scatters
a scattered
the original
in tbe refractive
that because
should va~
(in the region
the electrons.
of
with a scattering
radius,
is defined
N electrons
are small
should be proportional
In addition,
detect-
showed that the intensity
independently,
it is customary
should add to give
by following
in which there
Gordon4 predicted
section
into 4n solid angle.
d“e to the random motion of the electrons.
as a consequence
electron
calculations,
containing
and the powers
can be reached
gas a plasma
Gordon
scatter
Gordonl
a weakb”t
(i)
this cross
in radar
For a volume
will be independent,
This
because
whereas,
is 4. Ue.
In i958
at the ionosphere,
X10-13cm)2
has arisen
into unit solid angle,
electrons
that the electrons
but only
inGaussia””nits
= (2.8
tionto
directed
might he obtained.
by assuming
physics,
to study the ionosphere.
Ue given by the square of the classical
Some confusion
METHOD
has long been known in classical
powerful
the echo can be computed
cross
BACKSCATTER
use been made of this effect
that if avev
able echo from
F-REGION
“}
iNTRODUCTION
I.
OF THE
of 4%Mcps.
This
succeeded
equipment
with an aerial system
5
an area of about one acre.
Bowles
made the
to the predictions
1
together
of Gordon,T the echo spectmm
was very
of
. ..———
tfe correctly
,Iarrow.
macroscopic
bility
density
compared
attributed
variations
Of the elect rOns.
to the ions are cOmpelled
any part of the plasma
by the Debye
this tO the presence
electrically
Of the iOns in the Plasma
That is,
the electrOns
that cOntrol the
which have a high mo-
by cOulOmb fOr~es tO move in a ~aY wbich will
neutral.
The range Of these cOulOmb fOrces
keep
is characterized
len@h AD given in
i;==
(2)
,
4.rNe2
where
k is Boltzman”’s
constant,
the c:harge of an electron.
i.e,
m~,ch shorter
to the density
considered
theory
the result
mal velocity
of the exploring
in the electron
gas impressed
to take this effect
of an imaginary
of all ion.
The spectrtlm
nlore
recent
plete treatment
t~,rnecl signal
theoretical
Hagfors9
of magnitude
is shown in ‘Fig, t, together
1,0
be characterized
‘
with ‘Iwings”
Farley,
profile
and the therby a Gaussian
by Gordon.*
5 <.,7
DOughertY
correct.
shows that the strength
and further.
at the eclges.
with the Gaussian
colild be
of an electron
t~6predicted
by Fejer,
interactions
by Gordon,l
B<>wles5 mod-
that the scattering
shown that this %rie~vis not strictly
of the electron-ion
but flat-topped
narrower
the ~vave is sensitive
of the ions.
section
wo~,ld still
of this problem
ha”e
should be only half that predicted
tr~,~n is not Gaussian,
sPectr,tm
investigations
Ic, 11
and Salpeter
of the problem
As a result,
by the motion
having the cross
of the echo power
clensity at,d e
AD is of the Order of a few millimeters:
wave.
into account by postulating
particle
f~t{~ction, b~lt one which is some two orders
and Farley,8
N is the electron
temperature,
In most parts of the ionosphere.,
than the wa”elen~h
flLlctuations
ifiecl C,ordon’si
T is tbe electron
A com-
of the re-
that the shape of the spec -
The theoretical
for comparison.
form
of this
The wings of the
~
D, 8 —
0.6
0.4
—
Fig. 1. Thenormalized
power spectrum of thermal density
fluctuations(o)
for .Collisionl.ss
gas of neutral particles of
mass ~i, a“d (b) for the electrons in a collision [ess plasma
in which the ions have moss mi. Curve (a) has the same
shapes
thepower spectr.ms.ggested
by Gordon] whos.pposed tha+mi was them. ssofonelectron,
thereby givinga
—
Specfrum muchwiderthon
(b) (Ofter Dougherty Ond Forleya).
b
0,2
0.0
—
I
1.0
2.0
3
DOPPLER SHIF1
[orbilr.
ry ..its)
2
—-
.. . . .. .——--...—
-
spectrum
correspond
ro~>ghly to the Doppler
of sound for the ions.
damped
sound waves
One is their
wide
Thtjs,
own thermal
motion,
The discovery
of the narrow
proposed
at nlillsto!?e
small
Hill early
sections
measurements
macle early
work,
11.
dzd re”iew
are obtained.
in 1962 are also included.
The Millstone
(7i.5”W,
by Pettengill
rameters
a very
the pulse ceases
the echo intensity
pulse was used,
density
profile
density
decays
(Table
profile
witha
different
when
density
measurements
phases
of the
Massachusetts
solely
to the beha”iorof
profile
obser”ed
(75km)
under these conditions
wo”ld
but would yield
stlch
Above
Thus,
pulse would per,mit
less echo power,
some compromise
below
Hill,
between
a fixed
500km was obtained
of the ray path and tbe ionospheric
be to keep the antenna pointed
of pulse widths,
Since 75ktn
below about 500 km.
In most of the work at Millstone
approach
wo”kl
at the peak of the F-region,
The “~e of a shorter
of the regions
employed
when the antenna is
height of >i50 km, a“d the finite width of
density
to the pulse length.
of some of tbe pa-
pulse 75km in length.
for all heights
greatly.
The choice
The pulse length (500 psec)
square
with a scale
profile
1).
height i,,terval
of peak electron
resolution
with a variety
but this procedure
since
resolu-
500-psec
by reducing
layers
became
at the zenith and
would call for corresponding
bandwidth.
For most observations
conducted
represent
are related
comment.
large
so that the intersection
An alternative
in the recei”er
therefore,
parameters
to a very
must be sought.
and improved
make observations
also were
this site,
the density
is proportional
the antenna elevation
obtuse.
distorted
of the region
tion and echo intensity
an account of all tbe electron
,Iear the town of West ford,
and calls for
density
density
to distort
examination
made in witlter
res~]lts of some spectrum
than the scale height of the ionization
the ionization
data has yet been p~lb-
measurements
latitudes.
The facility bas been described in some detail
18
~ ~.
so that the description
of tbe equipment gi”en here
The electron
of thetr~le
as or larger
a long pulse yields
this height,
Preliminary
is located
from
corresponds
upward.
be the convolution
is as large
facility
1 is not obvious
vertically
all the available
density
paper provides
to a table of the equipment
in Table
con,nlenced
and Data Reduction
Observations
for most observations
tc>
in dialne -
MEASUREMENTS
at northern temperate
i7
and Kraft
and Arthur,
will be confined
it possible
ca!] be used for these meas”remetlts.
Since these two topics
PROflLE
Hill radar
42. 6-N).
the ionosphere
makes
than the one (3OO meters
and disct, ssed separately.
of Observation
Methods
part of the spectrum
Hill radar
the electron
The present
A.
changes
movi]lg
echo spectrum
as a Ineans of study ing the ionosphere
made up to the end of i961.
DENSITY
more
to a narrow
slowly
,I]lder the CIirect ion Of hlr. 1’. C. Pineo.
Since that time several
t2-i5
Most of these reports deal with
ELECTRON
a better
would cause a very
hy the more
of the work ha”e appeared.
they will be presented
directed
rise
smaller
at>d no paper presentitlg
one report
the best results
of the central
backscatter
in i960,
aspects
of the resl,lts,
16
tho”gb
form
ThLIS, the#Iillsto,,e
of incoherent
on particl,lar
lished,
than that of the ions,
n>otion is impressed
with an antentla tionsiderably
by Gordon.
Observations
reports
at the velocity
that which would be caused by greatly
This second motion gives
forces.
mo”ing
may be thought of as having two motiotls.
being higher
The second
by electrons
at the radio fl.eq~let?cy.
~,~easure these echoes
ter)
which,
broadening.
ions by means of coulomb
resembles
The electrons
in the medi~tm.
range of Doppler
centered
the spectrum
shift introduced
a receiver
bandwidth of Ilkcps
using both narrower
and wider
receiver
was employed,
bandwidths,
although experiments
A receiver
matched
3
.——-.
—
TABLE I
EQUIPMENT
PARAMETERS
OF
THE MILLSTONE
HILL
Parameter
Meas”remen t
Location
7J.50W,
Frequency
440 Mcps (68.cm wavelength)
An te”na
84- ftparabola
Effective
antenna
Ante””.
aperture
210*
gain
42.6°N
Beamwidth
2.10
right circular
(tro.$m itted)
left circ”[ar
500psec
frequency
bandwidth
Receiver
”oise figure
3 db (approximately)
Over-all
feeder
2 db (approximately)
to a 500-psec
11 kcps
losses
of the Doppler
&~.
waves were
backscatter
observations
effect
were
where
and the results
The signals
are generally
obser”ed
weaker
on winter
noise.
good results
days,
to obtain any useful
This is accomplished
weak,
NO
si~als
by the de-
of the transmitted
circularly
could
be
d~t~~t~d
~illman
et ~1.i9
have repotied
!—_
employed,
md use was made of
were
between
These
measure-
@ven height intervals,
because
they are more
are unobtainable,
when the critical
results,
way.
rarely
exceeds
Onwinternigbts,
night, ,b”t the quality
in the following
A filter
right-handed
and at best the predetection
to the peak of the F2-region
drops to a low “alue,
Tbe polarization
fading in the signals.
Hill,
that, for most
heights.
Similar
difficult
to in-
less useful,
than the receiver
tained during both the day andtbe
with that obtained
of electrons
measurements
(68 cm) are dictated
received.
waves
at Millstone
are exceedingly
tio ~f the echo corresponding
the echo is always
S
to introduce
total n“mbe~s
have not been undertaken
WaVe
width is required
in the receiver,
wavelength
and received,
polarized
in the earth, s ionosphere
one to compute
is employed
be changed,
and left-handed
linea~ly
for all F-region
although in most measurements
both transmitted
filter
spectrum
i“ this paper indicate
is about iikcps
and cannot readily
b“t a wider
The early
ones reported
and the operating
be altered,
transmitted
waves
tbe Faraday
measurements
power
system
can readily
when right-handed
precise
match to this si~al
transmitter
however,
of the signala,
width of the si~als
sign of the tran~mitte?
In order
a bandwidth of only 2kcps,
broadening
an approximate
The a“ailable
frequency
general Iy 20 db
‘2> ‘3 and the more
which provides
ments enabk
improvement
pulse would require
of the day, the spectral
terpret
(for these observations)
Receiver
as a consequence
polarized
(for these obser”otio”s)
50pps
Input signal-to-noise
ratio
through video i“tegrotion
wave,
(received)
2t02.5Mw
Pulse length
Pu13e repetition
horn feed
0,5db
Polarization
power
with conical
lom2
37,5+
Peak transmitted
of Pineo,
RADAR
frequency
a considerable
i:i.
ra-
At other heights
whentbe
In summer,
of the results
signal-to-noise
F-region
echoes
isgene?ally
critical
can be ob-
poor compared
is at ite highest.
amount of video
The output of the matched
integrating
filter
is required.
in the receiver
is
I
4
—
I
rectified
by using a square-law
received
power)
els.
is sampled
A “word”
detector.
The resulting
by means of a di@tal
representing
this level
are made at delay intervals
The samples
are synchronized
of 250psec
to determine
with the transmitter
the average
the system
gration
by an amount equivalent
processes
tinued for lotlger
runs preferable
drift-free
the samples
requires
tions of the E-region
from
– first
noise into the receiver
relative
to the height of the mean noise level,
temperature
These
must be computed
about –7db.
numbers
density
in which only receiver
since it requires
vs height profile
the computer
mean receiver
noise power
is next computed
of its range
(R2).
duced data points are displayed
(measured
density
of the
during
observa-
can he seen the
coupler)
a pulse
pulse rep-
the height of this pulse
ratio
the effective
of the echo corresponding
are required
if the density
along the abscissa).
from
computer,
of the
First,
is somewhat
is fheinterference
The range
to each sample
out in the form
prod" cedbycert.i"
is small.
The
R corresponding
up by an amount proportionalto
along the ordinate)
considerably
subjective
line in Fig, 2(a) beyond the F-region
of the antenna and the curvature
The R2factor
rep-
the measurements
the mean of all the samples
all the samples.
is scaled
the height corresponding
vertically
the numbers
also reduces
but the chance of error
in Fig. 2(b) and printed
(measured
*Apotiic"larly
vi.io.s
variety
neor the molar frequency.
and prevents
that (in this instance)
This process
to move the vetiical
ill the averaging,
and each sample
Finally,
way.
is obtained.
is then subtracted
being made for the elevation
shows electron
obtained
The calibration
From
The computer
in the following
operator
to each sample
lowance
out.
noise was measured
echo so that this will not be included
square
i443.5EST
absolutely.
points in Fig. 2(a) are printed
to an electron
of
The square pulse further
base.
one can conclude
anal-
the gated portion
(via a directional
When the punched paper tape is used as an input to the CG-24
resentingtbe
short
left corner
are samples
of 200km
temperature.
These
be~nningat
Beyond the ground clutter
was about 620”K and that the sipal-to-noise
to the peak of the F2-regionis
electrons
period
The spike which follows
of the time
receiver
con-
2(a) shows the summation
and then the F2-layer.
on each sweep
in the effective
The inte -
make se”eral
At the lower
out to ranges
of
the sums of the samples
Fi~re
pulse caused by introducing
a iOO”K increase
ratio.
although it is rarely
interference*
the base line.
extends
the sensitivity
si~al-to-noise
siflificance.
was gated off.
resents
receiver
proc-
this integration
improving
of i5° for a five-minute
the E-region
along the time base is a calibration
of broadband
Generally,
out on punched paper tape for later
when the antenna is at the zenith.
the ionosphere
in the
of m integration,
line has no special
which usually
and stored.
so that they are taken at
indefinitely,
of etiernal
[Fig. 2(a)] and printed
pulse when the receiver
lev-
can then be added together
thereby
less than a minute to complete.
The vertical
is caused by ground clutter,
almost
forms
can be seen four dots which represent
the transmitter
echoes
Various
taken with an antenna elevation
1961.
delay.
sweeps),
At the completion
on an oscilloscope
on 7 October
picture
at each given
(i5.000
compute~
frequency
The words
to 20.8db in the predetector
than i5 minutes.
This process
to the CG-24
repetition
and can be continued
to one long one.
are displayed
ysis.
power
of 5 minutes
to the
one of 256 possible
along each sweep of the radar time base.
the same points along the time base on each sweep.
computer
(which is proportional
and assi~ed
is then transmitted
The samples
ess is continued for a period
voltage
voltmeter
plotted
increases
oir.roft
is computed,
of the earth.
of stable.
These
Fi~re
the
with alre2(b)
aa a function of height
the importance
which carV
radio
of the
.Itimeten
tuned
I
5
..J
Fig. 2(a-b).
In (a)theobsewed
echo power osaf.nction
of range
is shown after five minutes’ integration.
The square pulse toward
thee.dof
the time base is.
calibration
signal.
The points in (b)
represent the electron density (along the ordinate) as a function of
height obt.ined from the data in (a).
6
—
I
F2-r+on
ini-slat?onto
gressively
larger
B.
at greater
measure
altitudes,
1960 observations
the signal
1960 were
suitable
servations
were
because
urements
in]ental
spectrum)
the errors
ass6eiated
with the points become
as can be seen by the increased
of equipment
aspect
seems
scatter
(or sometimes
malfunctions
Also,
pro-
of the points.
profiles
Therefore,
halfuf
196%, the followinE
Tbe receiver..bandwidth
(2)
A pulse length of.5.00psec
were employe d..
(3)
Two five-minilte
and 15”,
the data obtained
to obtain a single
and the three
runs were
density
Beyond this,
not all the profiles
to present
greater
yield
3 through
obtafned with a 2-kcps
be in considerable
errOr
inac-
i6)the
bandwidth
in the regiOn
Of
presented
were
epetitionfr
In these instances,
extend over
a period
to the three
parameters.
convenient
of the F2-region,
ical frequencies
in this report
were
then plotted
at 45” elevation
On each profile
manner
obser”ed,
the results
electron
to establish
density
On two profiles,
(Fig. 17).
points,
interval
to be deri”ed
electron
data,
E-echoes
peak,
most
over
from
a knowledge
Virginia
(77.5”W,
39.0-N),
The data used are the ho”~ly
.—.
—.-
on the
there
is
and
tO +20 percent,
generally
is foF2,
in %960, values
the peak
together
of the crit-
have been used and these
values
closest
to the time
1
.,,-.. -...——-...,.
obtained.
of the echo power
at one height,
measurements
the F2 peak
were
fashion,
are only accurate
density
the elec-
but tbe scale
in this normalized
Shown on each of the profiles
For the early
at Ft. Belvoir,
to normalize
Figs, i2(a-b),
sporadic
to the F2-region
are presented
the absolute
by a “B” in parentheses.
strong
since such measurements
appropriate.
—
are used
to a height of about
the time
it is convenient
because
was again normalized
by means of ionosonde
observed
they
contain so many experimental
inns.
in a uniform
Indeed,
and foES where
90”,45-
of about 40 min”tes,
elevations
peak of the F2-layer.
Because
little need for the absolute
the equipment
of 50cps
A mean was taken of the two runs at each elevation,
five-minute
density
the density
was changed.
equericy
made is stated.
totbe
electron
was established:
weight was given to the points taken at 45” and 90 DeleVati0n
the profiles
with respect
was not the greatest
are indicated
During many obser-
made at each of the elevations
profile.
the mean of two or more
In order
it is more
observations
ilkcps,:
and ap”lser
in this fashion
electron
which the measurements
abscissa
to that time the exper Thus,
the pro files:: (Figs.
was drawn so that it fitted the points obtained
400 to 500km.
tron density
Prior
method of taking measurements
wassetat
sets of points corresponding
A mean cur”e
represent
val-
way Of taking the meas-
and these measurements
Profiles
= 90”) are lik.ly.to
(1)
Although
proved
during the Ineasurements.
was employed.
on each:sf
stated.
in
density.
Dur.ing the latter
Although
obtained
sbtail>ed in 1961 when ob-
in progress.
taken only in the zenith,
(See.11-A).
!e. g., to
in addit”iOn tO tbe il”-l~cPs bandwidth g?.n-
set of antenna elevations
were
of 1961.
investigation
bandwidth and antenna elevation. are
peak. electron
only i9 profiles
were
not recognized
bandwidths” Of 2, 5 and 40kcPs
no specific
investigations
though some measurements
until the middle
by the particular
and/or only in the zenith (elevation
with foE,
b~weekly),
special
Thus,
basis.
of the results
which were
to have been established
vation perio~s. measurements
receiver
than on a. routine
The remainder
of certain
of the wOrk n.epOrted here is that nc systematic
were made with ~e~eiver
density
made for the purpose
rather
for inclusicn.
method was dictated
erally..l>sed.
were
made weekly
One unfortunate
curate
Also,
The Obser~ations
During
ueless
the E-1ayer.
,.-
---
K
/
t
~
KP=Z+
Kp .3-
~
I
,
II
IIIU
I((1
I
1,,
!
,,1
(.)
;
.
1
,
11!11
(b)
~
Y
:
‘\
\
\
\
\
.00
I, MARC.
,436-,444
,,M.RCH 1980
,550-1621
.0.
EST
,,,0
EST
,5- ELEVAT!ON
,5° ELEvATION
?,,,,
2,.,,
,ANDW,DTH
10F2=I!
L
3MC,S
,. NDWIT.
,0 F,= II.O MCP, 181
h
(B]
I
I
/
NORMALIZED
Fig. 3(a-d).
techniqueot
Electro.
Mllstone
densiVprofiles
Radar.
ELECTRON
obsewed
8
DENSITY
[P. rc.”t)
bymeans
of the incoherent
backscatter
\ 3-3!4-7326 [o-d,
\
1, .,,,,
,,s0
,QOO-(+20
E,,
\
\
I
19 MARCH 1960
,44,-,456
E*T
,,a ELEvATION
, ,0,s 9A ND WIDTH
15e FL E”ATION
2 kc,, BANDWIDTH
\
\
\
\
\
\
\
\
\
fo,, ~(lo. cpz
(s)
400
fo,, ~!o,,
.,,,
[B)
\
I
200 -
t
:
,3 J”LY
E
ZIE330°
‘\
!960
2220
EST
ELEVATION
5kCPs
BANDWIDTH
1960
,002-(085
30\
‘\
EST
\
ELEVATION
, ,.,s
BANDWIDTH
\
.00 -
‘\
,.,,
400
IA”G”ST
\
=7,4 .,,,
(B)
\
~_
/
200 –
K,= 2+
K p=30
~
I
I
,
1,,
,
,.
1
I
,
1111
80
ii)
(C1
NORMALIZED
Fig. 4(a-d).
Electron
technique at Mllstone
,,1
density profiles
Rador.
ELECTRON
obsewedby
9
DENSITY
(Pa,Centl
means of theincoherent
backscatter
IC
\,
,,”,”s,
2,07-2,3,
,,,0
r,T
90- EL E”AT, ON
5 “,, s 8L. DWID, H
\
f. s,
\
\
I
‘,”
1
,
111111
I
1
2.
I
(b)
r
r
\
t
I
\
\
2N0vEM0ER
(960
,,50,605E,T
45~+,o~ELEv,Tlo,s
1( kc PsEAND WIDTH
,.,,
.,O.
O,,,$
,,)
I
1-
1
I
L
.0...,,,..
Fig. 5(a-d).
Electron
technique of Mllstone
density profiles
Radar.
SLFCT RON DENSITY
(Psr’. ”!)
observed by means of the incoherent
backscatter
II
600
400
T
!, DECEMBER ,,60
1, DEC, MBER ,960
,,,,
- ,54, ,s,
,o~ ELEVATION
,,,,
,o~
,,,.,,
40,.,,
,,...,,,.
c,,
ea...,,,,
\
I fg,,
~,.o.
-,6,6
,s,
ELEVATION
\
{B)
,.,2
.,0.2..,,
,,)
,\
2, ,,,,.8,,
1,,8
-),
,,,0
$3 EST
~
II
,.,
,0,...,,,0
Fig. 6(a-d).
Electron
tech”ia”e at Mllstone
,,,,,,0.
,,,,,,,
density pro files obsarvedbymea.sof
Radar.
,,,,,,”,,
the incoherent
bocks.atter
:1
t
,1 DECEMBER
,.53- (7(3 E,,
2,
1960
45° ELEvATION
2 k,,,
8.,,.,.7,
,00
t
.,,,.,,.
,,,0
(1, +-, t23E,T
,0- ELEVATION
,,+
,skcps
BANDWIDTH
\
,OF, =S, OM<PS [B)
‘O F,=
\
681M$PS
I
{B)
L—
/
“’~—
:
300,,,.,,,
\
[9,0
600
1, ,.,
\
,4,,.,45,
,s7
86- E,. ”,,,..
2 kc,, OAMDWIDTH
,,6,
”.,”
;;?;F;:;N
\,
II ,.,s
6ANOW ,0TH
\
400
,.,,
= ,0,0 M,,,
[6)
foF, =8.6
Me,% (M.
,0,, =..,
.c,s
)
(B)
\
\
I
I
,.
.0,..,,,,0
Fig. 7(a-d).
Electron
technique at Mllstone
ELECTRON
DENSITY
[,<?,.”!1
density pro files observed bymeonsof
Radar.
the incoherent
backscatter
\
\
7 FE BR”ARY
1961
,325 -,,46,,,
90~ ELEVATION
II ,.,s
\
8ANOWIDTI
-
‘\
2!,53‘ARCH
“6’
,4+7 EST
\
4$- EL E”ATION
\
( ( ,.,s
BANDWIDTH
\
\
\
20.
1’
Il!)ll
5
(:,
,
fof,
,7.,
,0 F, =,7
,\
MCP5 (M. ]
MC,.
(0)
I
‘.6
=3.0
M<P, (B
M H)
L<
,,=,.
I
I
I
,0
NORMALIZED
(c
ELECTRON
Fig. 8(a-d).
Election density profiles obsewed
technique at W I I stone Radar.
DENSITY
l,cr.e”l)
by means of the incoherent
backscatter
,3 MA*CH
,,,,
l\
,54,
-,,,0
ES,
45.+50.
II kc,,
foF2=7,5Mcns(B,
EL, V, TIONS
BANDWIDTH
M H)
.0=3.
1,,
,,1
I
1
~~1
.,=2+
1,,
,
,,1
10
(c]
!
1
50
NOR.. LI2ED
,
,0.
,.,
ELECTRON
DENSITY
(,s,..,,)
Fig, 9(a-d).
Elecko” density profi Ies observed by means of the incoherent
technique ot Mil Istone Radar.
bocksc otter
\
\
6.0
I
5 APRIL
\
,04,
,, ,,,,,
E*,
\
,,,,
,650-,.55
5,.
Ilk,,,
\
\
ES,
,LE”A,
ION
,a,,w,,,,
\
\
\
\,
..,s
=6,,
‘\
\
\
(M .,
,\
I
‘J
foE=3.1MC,,
1
1
(
I
,.,
)
I 1 Ill
(.1
I
,,= ,.
t
1 I
1,,1
1
28 APRIL
\
1I d
,96,
,53,-,,0,
1, ,,,,
1
‘\
EST
I
,
BA,,
w,o,
28 APRIL
\
,6*2-1647
\
I
I I
1
.00-
,8,
136,
EST
90° ELEVATION
1, ,,, s BANOW, OTH
Y
”
-
foF2: 78 M.,,
1 I
[b)
\
.0,
,,,,
-,0,,
20~, SO- EL E”AT,ONS
,, k,,,
8A ND W,DTH
\
,.,2
,.0
r
‘\
‘OF, .7,5
..,,
,.
foF, =7.3
.,,,
[B)
1
*oo–
~]
1
,,. ,-
~@
NORMALIZED
ELECTRON
Fig. 10(a-d).
Electron density profi Ies obsewed
technique at WI [stone Radar.
OENSIT.
5
[,..,,.,,
/:)
by means of the incoherent
,0.
backscotter
\,-314-?,33
(o-d)
I
,o$~,o.
cp,(..
;\=,
, .,,,
l
[6)
\
I
,
.1
K0,3+
\
\
\
\
,, ,“,,
,,6,
,0,0 -(0,5 ES,
,0°,L, vAT(o.
40,,,,
BANOWIDTH
\
,05: 5.2 M<P, [M “)
$$.6.
L
,0
(,,
\
\
OMCP, [B)
5.
Fig, 11 (a-d).
Electron density profi Ies observed by means of the incoherent
technique at Ml Istone Radar.
bockscatter
i6
—
2, JULY ,961
,00, -,0,,
ES,
26- ELEvATION
,1 kc,, BANDWIDTH
.0.
\
\
\
\
\
“i.
\
‘\\
4.0 -
“D=‘0
I
I
Il!ti
,0
!
1
‘o
‘,.
Ill
1
1
1111,1
1
50
!00
)
1
I
I
)
I
I 1,
,.0
[b)
(0)
\
1,
&uG”sT1,6,
,020-$035
E? A“GUST
\
,+52-
EST
,A.
DWIDTH
\
15,7 EST
30-+s50
ELEVATIONS
II ,.,,
SANOWIOT”
BOG FL E”ATl ON
II ,.,,
(961
..0
\
\
\
400
,/
foF2 =70 MOPS(8)
1
t
NORMALIZED
ELECTRON
I
!
1,1$11
5
;:)
I
DENSITY lP.rce”t)
Fig. 12(a-d).
Electron density profi Ies observed by means of the incoherent
techni~ue at WI Istone Radar.
i7
I $ I(I
,.
,0.
backscatter
\
\
\
‘\
29 A“GUST
,323-,346
30°+870
,, ,.0,
\
\
\
5 SEPTEMBER
!96,
(444-
,,,
,506
,,6,
\
ES,
,O” ELEVATION
ELEvATIONS
II ,.,,
BANDWIDTH
,ANDWIDTH
\
\
foF, =6,3
,0F2= 5.9 MGP6 [MH)
‘.,,
foF*=57”tp’~’}
McP, (MH)
=6.5.,,,(,)
,\
\
I
I
faE= 3, MC,%[MH1
faE
,(
= 3.35 McP$1BI
/
/
‘\
\
\
‘\
\
“\
(Z SEPTEMBER
1409 -15!4
,O”+
,$6(
\
26 SEPTEMBER
,0,5-
EST
I(O8
,36,
<ST
,o~+45~+s9~
85° ELEvAT, OWS
,,,
”,7,0.
s
11 k,,% BANDWIDTH
1, kcp, BANDWIDTH
1
\
,.,, =,.9
\
,.,,
.,,s
(..)
= 7.2 M.,,
(B)
+
~
,
(C1
NORMALIZED
ELECTRON
DENSITY ( P,,.,.,
,0
(d)
,0
!0.
)
Fig. 13(o-d).
Electron density profi Ies observed by means of the incoherent
tech”iq”e at Mll$tone
Radar,
bockscatter
\\
\
I
‘\
\
1
5 OCTOBER
!424-
)503
1, OCTOBER
>96!
0734
EST
,5 °+45-+s00
-08,5,
,LEVA,!O,S
,, kc,,
II kcP, EANDWIOTH
\
s,
,,~+,,.+.,.
ELEvATIONS
\
,96!
\
BANDWIDTH
\
\
‘OF,=64MCPS(MH)
‘.F,=721M~,~(B)
,.,
=2.,
,.,
= z.,,
.,,
\
s,.,,
MC,, ,8)
,OE = 2.,..,,,.”)
,.,
= 2.6 ..,,
L
[B)
\
/
/
\
\
\
\
20
OCTOBER
,412-1449
,
NOVEMBER ,,6
0908 -09!9
EST
\
EST
(,~,45~+89~
,, ,.,s
(96,
.,.
EL E”ATION*
,,,
II ,,,,
BANDwIDTH
\
I
\
”,,,0.
B. ND W,DTH
‘\
\
,OFZ=,, ZMC,S(MHI
‘o’,
= 8DMCP’
~’ ]
ioF, = 7.0 M,,,
foF2=67Mc,
h
[MHI
s19)
,\
I
K, -20
,p~o+
,
I
!
11!
,11
1
1
1 11111
,0
lot
1
I
1,,
,
,,1
)
50
!<
(1:
(Lo,
NORMALIZED
CLEC, RON DENSITY
Fig. 14(a-d).
Electron density profi Ies obsewed
technique at Ml Istone Radar.
(,,,.,”9
)
by mea”, of the incoherent
backscatter
13.314 .?331(o.
d,,
~
\
\
\
\
\
2 ,O” EMOER ,,61
,53,-,.0+
EST
\
,,~+45~,,o.
,,,,,,,,
1, ,,,,
,0 NOVEMBER
BAbiG!v DTH
0s5,0
,,..
\
,30
.5.,
II kc,,
196[
EST
,.-
E,, ”,,,.,,
BAI, DWIDTH
\
\
I-—
........
‘“”=w
‘P=
‘P’ ‘o
‘.
.~.
6..
I
I
1
I
1 Ilud
1
1 Ilu
[,1
‘\
‘0
‘0”’”’”
,s27- )653
\
\
,,~..,~,,o~
‘9”
2,
EST
NOVEM8ER
,545-,,50
ELE”ATIO,
.,.
\\
,,,,
EST
EL EVAT,ON
II ,,,s
BAMDw,DTH
\
\
/
‘a F,=65MC0$(MH)
‘, F,= ’’MCo’
(B]
\
‘/
,.
,0,..,,,,0
ELECTRON
DE
NS,,”
(,,,,,
”,)
Fig. 15(a-d).
Electron density profi Ies observed by means of the incoherent
technique at Ml Istone Radar.
20
backscatter
33,4 -?3,8{ .-.)
\
\
\
‘\
\
\
.0.
–
28 NOVEMBER
,OOs-
40.
,045
,96,
7 DECEMBER
1437 -,5,0
EST
,96,
\
EST
\
1,~.,,.+,o~,,rv.,lo,s
15~+45~+,o~ELEvA,,oNs
1, kc,<
(1 kc,,
BANDwIDTH
‘
BANDwIDTH
-
f, F,=~2MCPSl
‘o ‘2=
,OE =2,8
MH)
fOF2=7.2M<Ps
[M”)
,0 F,= 7.6 M,,,
h
(,)
7“0~._._
‘oE=25L/
McP$ (8)( M”)
200
27 DECEMBER
,05,
60,
l,.
-,,,5
1961
EST
EL EVAT$O.
1, kc,,
BANDWIDTH
‘\
\
\
\
,0F2=8..
MCP,
(M
.1’,
,0,2 = 8.8 ..,,
I
I
(,)
\
I
fOE -2.3
Mc,s (MH)
,OE = 2.9 .,,s
(6)
<
Fig. 16(a-c).
Electron density profiles
techniaue at WI Istone Radar.
observed by means of the incoherent
bo.kscatter
Fig. 17.
The electron density profiles observed on
20 October 1961, when o 500-psec transmitter p. Ise
wos employed and observations were made at the
three antenna elevations designated.
~~,-o
ELECTRON
o“er
DENSITY
which the backs catter
ionosphere
[ocbilrary
observations
along the ray path fairly
(corresponding
to the bearing
in %96$ a C-4 ionosonde
ical frequencies
In general,
they differ
were
obtained.
obtained
These
piece
in the Journal
The undesirable
tion only 26 km.
effect
The recei”er
due to this convolution
at the three
arbit raw
spheric
tests.
exist
were
obtained
soundings
at 45” elevation
(Figs.
from
Early
for the crit-
in parentheses.
and where
3 through
i6) is the
the geophysical
errors,
rocket
data
the results
Bowles5
profiles
as shoti
to estimate
of, 90°,
The finite
bandwidth of
as *OOpeec were
source
trend of the
of error
Clearly,
employed.
is the
the profiles
their magnitude.
is to compare
them with other electron density
20
et al.,
have compared their backscatter
and Millman,
Howe”er,
and ionosonde
which
an elevation
as the progressive
An additional
(up to the F2 maximum)
profiles
For
measure-
52 km, and at %5” eleva-
a final curve through these points.
i8 through 20 the most accurate
pared with the backscatter
until pulses
shows in Fig. i7.
and found good agreement.
between
earlier.
at half these intervals.
effect
b“t it is difficult
profiles
pulse used in these
it occupies
in the shape of the profiles,
elevations
of the F-region.
with density
In Figs,
in each diagram
values
has been mentioned
output is sampled
The best method of checking
by Nisbet24,22
by “MH”
made.
are in good agreement,
of the long ( 500-psec)
of 75 km;
method of drawing
of systematic
observations
were
values
Research.
kcps) would have negligible
obtained
measurements
in the
appropriate.
These
of electrons
a height interval
Errors
somewhat
measurements
in the diagrams
contained
index Kp.
of the convolution
curves
are not free
seems
the conditions
at an azimuth of 220”
Hill and additional
Hill and Ft. Belvoir
of information
ments with the true distribution
the pulse occupies
(ii
at Millstone
are indicated
at Millstone
of Geophysical
should represent
of the Results
Accuracy
the receiver
They
when low elevation
mean of the two “alues
The only additional
C.
made.
since the antenna was directed
of m. Belvoir)
the values
a simple
were
well,
was put into operation
value for the planet ary magnetic
presented
““!1$)
22
from the reduction
in “i,ew of the discrepancies
results,
available
correspond
obtained
of ionoobserved
perphaps
rocket
this is not the best of
23-26
profiles
have been com-
most closely
in time of day and year.
,000
so,
~
r\-.-_
.~
: ,AcKcAT:~::
600
:;1
‘1%30
EST 2 NOV ,960
40. -
’00
~
\\
.,
‘:
,,,,1.,
0,00
‘K>.
\\
N
>=-”’
EST 10.0.
1959
Fig. 18. The results of a single b.cks.atter
run during November 1960
compared with the results of rocket soundings from Wal lops Island,
Virginia.
in November
1959 (8erning24)
and November
1960 (Hanson
and McKibbin23).
\
60.
g
g
:
-
k
.00
1,
‘\\ \>
~;:E::;zE/’\f
-
\\.
\
BERNING ROCKET PROFILE
‘0947
EST !3 JULY 1960
\
L
I
Fig. 20.
for July
~b+ai”ed
Fig. 19.
The resulk of a ba.kscatter
run in
April 1961 compared with the profi Ie obtained
from a rocket sounding from wallops Island,
Virginia,
on the previous day (Jackson and
8auer24).
before.
23
—.
The resul b of WO bockscotter profiles
1961 compared with a rocket profile
bY 8erning25 in the same month a Year
Unfortunately,
in two cases backscatter
not obtained
in the same year;
two instances)
good agreement
rocket
hence,
with backscatter
in every
profiles
rocket
profiles
case,
is sufficient
results
which could be compared
data taken one year
obtained
but the degree
to suggest
a year
of similarity
that neither
OF F2 ELECTRON
DENSIW
10.0
NF2/.NE
from Backscatter
10.7
15°
24 Mar 61
7.3
3.8
90”
28 Mor 61
7,3”
4.4
20”
5 Apr 61
4.8
1.8
20”
22 Aug 61
4.5
2.0
30”
29 Aug 61
3.2
1.1
30”
12 Sept 61
3.0
1,33
30”
3.6
15°
5 oct
61
6.9
I I Ott
61
5.6
3.0
I 59
61
7. I
6,6
I 50
61
9.7
11.1
15°
10 No” 61
7.1
4.2
15°
10 Nov 61
13.8
9.0
15“
6.25
4.2
I 50
7 De. 61
9.0
7.1
15°
27 De. 61
11.6
9,0
I 5“
test which can be applied
against
one can check the ratio
those inferred
E- e,cho are ignored,
records
are listed
E-region
density
the observed
the expected
to these
from
there
in Table
NE expected
their
results
from
and expected
are eighteen
the ionosonde
ratios
antenna ele”ation
is to examine
of the electron
critical
II, which @ves
agree
them for internal
densities
frequenciess.
that exhibit
the ratiO Of the F2-electrOn
density
NF2 ‘0 the
data and alSO tO that actually, Observed
In five
to within *2O percent.
were
about twice
that actually
All these records
In the remainder
observed.
(1)
The F2 peak, being sharper than the ledge caused by the E-region,
suffer more because of the convolving effect of the long pulse.
(2)
For elevations
above 20°, weak ground clutter
the same range as the E-region
echo, thereby
high value Of NE.
24
-—--
a
Others that shOw bOth F2- and E- TegiOns,
There
causes for’ this discrepancy:
.—
consist-
at the peak of the E- arid
If the records
of i 5“ had been employed.
ratio was on the average
and
error.
Lowest Antenna
Elevation
Data
45°
obtained when a lowest
—
‘E
450
For instance,
possible
DENSl~
2.6
instances
ords,
systematic
4.0
Another
sporadic
the backscatter
9.0
28 NOV 61
These
between
6.5
~OV
expect
to large
2 Mar 61
2
F2-layers
observed
15 Mar 61
20 Ott
ency,
(in these
TO THE E-REGION
NF2/NE
19 Mar 60
have been compared
We should not, therefore,
II
NF2
from Ionosonde Data
Date
data were
method is subject
TABLE
RATIO
later.
with rocket
-.—.——
may
echoes may be present in
yielding an unexpectedly
of the re care four
D.
(3)
The presence of sporadic
E ionization may be responsible
fo= weak
coherent echoes which also increase the observed value for NE.
(4)
The scattering
cross section Of the electrons
between the electron and ion temperatures27
with altitude (Sec. 111).
Discussion
1.
of the Results
General
Se”eral
Considerations
interesting
features
a ledge in the ionization
caused in pad
i)?
height.
in summer
comment.
exhibit
a separate
to resolve
in any profile,
at these latitudes.
details
occupies
appears
maximum.
smaller
although it is present
We conclude
and hence that this ledge
The E-region
This
may he
than about 20 km
on ionosonde
that the resolution
only a small
as
records
was insufficient
height interval,
approxi -
10 to 20 km.
i August
1961).
electron
of Es can cause very
of some 2.4 times
sumed to be thin (-i
i,~terval
p,dse.
echo) by a factor
The ratio
to be somewhere
“f 2.4:i
either
density,
large
regions
density
seems
irre@lar,
Spread-F
morning
backscattered
dense,
acceptable
were
but no F-re@on
signals.
frequently
Thus,
ularities
in the electron
observed
in sporadic
a peak
pre-
the F-region.
existed
observed
echoes
it seems
Hill or tbe Ft. Belvoir
the paradox
like auroral
electron
to detect
which are responsible
records,
for spread
are catlsed by
these irre~larities
discussed
particularly
were
condition,
preciously.
during the
observed
(both in time as well
a spread-F
of electron
E-echoes
density
high intensity
that the resolution
by assuming
regions
only in a weak form,
on ionosonde
ratio
sem@Ohey~nt echOes
These
L8
This
latter
exionization.
the view that sporadic
of unusually
to that of the
to see an ohser”ed
or that irre~lar
of E-region
to
on this day appeared
the Millstone
which yielded
(relative
in the
as height)
avail-
and that the irreg-
F are not as great
as those
E.
I“ view of the above
profiles
from
thickness
We are able to resolve
When present
was insufficient
density
is always
would be reduced
we should not expect
but might scatter
high values
hours,
echoes
of the Es-layer
(-50 km),
and supports
echoes
E-layer
and tbe F2-region
upon whether
is thin.
of ionization.
to the unexpectedly
able for these measurements
t ron density
of the ratio
Thus,
with the wavelength,
the more
dense regions
may contribute
that tbe E~-echo
in the E~-layer
if the Es-layer
need not be critically
planation
therefore,
is as thick as the pulse
c~mpared
tbe Es echo indicated
to ionosonde
1:1 and 4:1 depending
for the densities
t9b4,
on 1 August was 45”, so that the pulse would occupy a height
data is taken as most appropriate.
that the E.-layer
on 1 August
it is usually transparent
of 50. because
of the electron
between
observed
(e. g., on 30 June i 9bi, 26 July 196$ and
The sporadic
We might expect,
of 52 km.
ionosonde
km) because
returns
that of the F2-region.
of the antenna employed
the F-region
strong
In the case of the profile
density
The elevation
scatter
deserve
of the measurements
is observable
its detection,
The presence
early
of these profiles
and does not usually
by the inability
during the daytime
mately
profile
NO F1 -ledge
to permit
is a function of the ratio
and, therefore,
decreases
comments,
below
it seems
about 200 km.
method may be able to challenge
unwise to place a great deal of reliance
When better
the ionosonde
value lies large ly in the ability
to obtain the electron
this feature
discussion
that the remaining
will
equipment
in this region,
density
be concerned.
,.,
25
becomes
a“ailable,
on the electbe back-
but at the present
distribution
above Nmax.
time its
It is with
2. The Height of Maximum
The re are insufficient
the profile
Instead,
profiles
shape (although Pineo
El. ctron Density
to permit a detailed examination of the diurnal variation
29
have attempted this for one day in May 196i).
of
and Hynek
of hmax and the scale
only the variation
hmax
height Hi of the ionization
above hmax will be
investigated.
for hm=x obser”ed
The values
are shown in Figs.
crease
21(a-b).
throughout
p“blisbed
imately
between
sunspot maximum
there
(taken as the time between
seems
to be a tendency
equinoxes)
for hmax to in-
and minimum.
1
I
1
13-314
-1342
[o-b)
I
SUMMER
400
,and winter
the day. The actual values are about what might be expected from the table
30
If allowance is made for the fact that the measurements
were made approx-
by Brice
midway
in summer
During both seasons
wINTER
.
.
Fig. 21 (o-b).
Values for the height of maximum density hmox observed in (a) summer and
(b) winter (taken from the curves presented
in Figs.4 through 17).
t
t
o~
~~
l,m
LOCAL
TIME
240[
LOCAL
[EST)
TIME
(EST)
(b)
[0)
3, Scale Height Hi above hmax
Some comparisons
profiles
obtained
mean height (280 km).
in every
case,
H.
can be neglected,
le”el.
profiles
as exp((i/2)[i
For values
were
– z - (exp–
particles.
height of the ionization
between
since insufficient
five morning
from
the data because
their
actual heights
day
to their
foF2 was iO * i Mcps
summer
profiles
Hi is of the order
profiles,
and winter
were
available
profiles
to divide
of fOO km, but grad~lally
as the time
the year
are stated.
have been adjusted
an approximate
frequency
1“ the morning
fit to the results,
fit.
26
Of One scale
(exp–z)
height that is twice
sec x
the scale
300 to 500 km
increases
have been superimposed.
above this
For this purpose,
between
the equinoxes,
into four seasons.
and Fig. 24 shows five taken in the afternoon.
profiles
a reasonable
scale
the term
that over the height range
was taken simply
The mean critical
(X = 30? provides
z is the height in units
and z >3,
with an apparent
Fig. 22 indicates
cause foF2 = 6.5 + 1 Mcps.
provides
adjusting
x of 60” or less
decreases
Thus,
In Figs, 23 and 24, some summer
the di”ision
selected
In Fig. 22, ten winter
after
z) sec x]) where
of zenith distance
and fbe density
height of the neutral
the scale
These
in Figs. 22 to 24.
together,
critical frequency was *O Mcps.
Also shown in Fig. 22 is a set of
31
a Chapman
re~on computed for a scale height H of 50 km and a solar zenith
i6
the electron
density in a Chapman re.
As noted in the previous
review,
~ of 60”.
gion diminishes
height
are provided
and the average
points representing
distance
of the profiles
in i960 have been plotted
Fi~re
All ten were
23 shows
selected
be-
and the mean height to which individual
a Chapman re@on
and in the afternoon
where
H - 65 km
H = 70 km (X = 30-)
,A\
780
/4 ,:
3
680
5ec
~
*80
:
“
:
38C
Zec
1
[8
MAR
1960
,400-1550
EST
P
2
NOV
(960
,550
EST
3
2
DEC
!960
8432–1455
EST
4
15
DEC
,960
,529-1550
EST
-[605
5
)S
DEC
1960
(621
6
20
DEC
,960
1002-(1(0
-[625
EST
7
2]
DEC
,960
1628-1653
EST
e
2,
DEC
,960
,653
EST
9
29
DEC
,960
1114–,,32
\
x
EST
-,7,3
\
\
EST
10
18[
e(
I
z
I
I
I
I xl
,0
5
20
FREOUENCY=!OMcPs
I
I
I
50
10
Fig. 22.
Ten win ter profiles observed i“ 1960 are superimposed.
The true heights have
been adiusted so that each curve reaches a maximum at the mean value for hmax.
27
I
‘\’\\
“
‘,
.
4
5
\\.
~
\
,3
440
t
z
:
> 340
\
–
“
~
E
❑
.
,40
I
A?.
,96,
,0+7
–
10S2
EST
JUN
196(
0947
JUL
,961
0827
— 1000
?
FST
–
0856
EST
3
7
4
,2
. . II.
.,,
1961
IOi O — 1015
EsT
5
,5
.“G
,96(
Io20
EST
CHAPMAN
REGION
-
1035
‘,
)
.
H = 65 km
(40 -
MEAN
40
CRITICAL
FREQUENCYI
2
,
1
1
I I 1,11
5
10
20
N/NmOx [P8rce”tl
1
Fig. 23.
Five summer morning profiles observed in 1961
are superimposed.
The true heights have been odiusted
so that each curve reaches a maximumot the mean value
for h
max’
I
6.2 M%,,
1
50
1
,00
.!
7,0
-
.,0
-
,20
-
I
.
3
I
Fig. 24.
Five summer afternoon prof i Ies observed in 1961
ore superimposed.
The true heights hove been adiusted
so that each curve reaches a maximum at the mean value
for h
max.
z
:
.20
-,
z
o
❑
r
5.0
-
II
APR
!96(
)650-1655
EST
2
~
22
AUG
196!
!~5z-
EST
5
SEP
!96(
1444-1506
EST
4
21
APR
[961
1551 ‘!602
EST
5
,B
&PR
196$
1S42-
EST
,
CHAPMAN
REGION
1517
)647
H = 70km
220
5
1
,20 MEAN
CRITICAL
FREQUENCY= 6.9 MCPS
20
1
2
I
5
1, II
10
NINmOx
I
20
1 1 Ill
50
100
( Perce.f)
28
.—
Mean values
following
way.
and 250
for the scale
The gradient
height Hi of the ionization
On each profile
km above the observed
winter,
and the day subdivided
level
roughly
ra,ldon,
assuming
errors
that the observed
of measurement.
s,dts are summarized
as a function
diagrams.
res,,lts
in Table
of this analysis
- square
aging the results.
HOwever,
Of values
.ase
FiWre
linear
divided
into summer
27 provides
in Table
with the estimated
represents
error
statistical
with height.
a representative
was next obtained
example
Tables
Ill and IV relate
certain
trends
are clearly
to the different
visible
The summer values
than those observed
They
the influence
of FIi averaged
i“ winter.
show that the ions,
of gravity,
and the
density
of production
are:
the value of Hi at
in the upper part of the F-reg:on
and recombination,
to seek a hydrostatic
downward,
These
of aver-
over the whole day are higher
that electron
in attempting
tend to move
in either
in bOth tables.
(c)
ha”e postulated
of one of these
methods
In summer there is a marked increase in HI and dHi/dh follo~ving
sunrise and a decline in both these quantities throughout the day.
by the competi,-,g processes
bringing
equilibrium
the electrons
but by mass mo condition
~
~
1500-(800
,,
200
300
400
EST
500
[d)
ABOVE
THE
LEVEL
OF fmax
F2
under
with them due to coulomb
]3-314 -734610-4)1
HEIGHT
re -
replotted
IV.
between
[b)
authors32’33
due to
These
later
for each diagram,
In winter there is little diurnal variation
a given height or tbe slope dHi/dh.
Several
AHi computed
variations
(a)
is not governed
and
The mean values for Hi ob-
lIi is found to increase
relation
in tbe
of 100, 150, 200
The data poirlts used in Figs. 25 and 26 were
are presented
Some of the differences
ti[>ns.
In every
III.
of their true height.
A least-mean
spread
were
equal intervals.
tained in this way are shown in Figs. 25 and 26, together
by simply
at height intervals
The profiles
of Nmax.
intO three
above Nmax have been obtained
was estimated
(k”)
Fig. 25(a-d).
The mean value of the scale height Hi obsewed at different distances above hmax
for (a) the whole day, (b) 0900-1200
EST, (c) 1200-1500
EST, (d) 1500-1800
EST in winter.
3-314-1341{0-s)
400SUMMER
.0700
.
DAY
(mea” of 011,,s.11s1
-1000
EST
/
rl
1400-1700
‘oo~
o
IoO
200
300
(c)
HEIGHT
400
s..
o
E
,00
200
300
400
EST
500
{d)
ABOVE
THE
LEVEL
OF
fro.,
F2
(km)
Fig. 26(.-d).
The mean value of the scale height Hi obsewed
above hwox during the time indicated (all taken in summer).
at vorio.s
..
“E(OHT h (km)
Fig. 27.
The values for scale height Hi plotted os a function
of true height h for the winter day period 1200-1500
EST.
The straight line is . least-mean-square
fit to the points.
30
distances
TABLE Ill
THE MEAN
VARIATION
FOR
OF N ~ax (h-hmax)
OF THE SCALE HEIGHT
Hi WITH HEIGHT ABOVE THE LEVEL
SUMMER AND WINTER BACKSCATTER OBSERVATIONS,
1960-61
Winter
Hi at h-h
max
(km)
Period
All day
170
09–12
167
Summer
dHi
= 250
AHi
●7
*I4
d(h-h
Hi at h-h
max
)
max
(km)
~eriod
dHi
= 25o
AH.
d(h-hmax)
0.40
All day
232
*14
0,36
0.42
07-10
309
+23
0.68
12-15
I 70
+8
0.35
IO-14
223
+15
0.43
15-18
155
*6
0.40
14-17
200
*lo
0.57
TA8LE
Iv
THE MEAN VARIATION
OF SCALE HEIGHT
FOR SUMMER AND WINTER BACKSCATTER
fi WITH TRUE HEIGHT h
OBSERVATIONS,
1960-61
Mnter
Period
h
max
(km)
Hi at h = 500
(km)
dHi/dh
Period
157
0.32
All day
224
0.26
09–12
270,5
158
0.25
07-10
230.0
304
0.%
12-15
297.9
156
0.25
10-14
268.8
21 I
0.42
15-18
272.8
152
0.30
14-17
273.1
I 97
0.29
-380
132
0.28
Al I day
Night
L
attraction,
Since the electrons
form their
own equilibrium
the distrib”tio”
achieved
are considerably
distribution
lighter,
and would in the absence
with a mLlch larger
by the ions.
The net result
scale
height,
is that the scale
their
of the ions
presence
modifies
height Of the iOniZatiOn Hi
is given by
k(T
Hi = ~
+ T.)
,
mi g
(3)
where
Te = electron
temperature
Ti = ion temperature
mi = ionic mass
g = acceleration
Bauer and Jackson26
ion diffusion
thermal
re~on
the conductivity
abo”e
,
,
due to gra”ity
have ar~ed
is the controlling
,
factor
that the rocket
in this re@On,
about 300 km was postulated
results
by Nicolet34
the atmospberi
and a constant temperature
35
However,
c mode 1 publisbed by Johnson.
Fig. la shows,
not all the rocket
backscatter
(c) the scale
in this region,
profiles
indicate
height Observed
all tend to increase
profiles
an almost
indicate
a constant
particles
In Fig. 28, values
equals
on theoretical
as indicating
a cOnstant
grounds
that
An iso-
concerning
for this region has been assumed in
46
bas pointed out that (a) as
the author
constant value for Hi,
fOr the neutral
with height.
can be interpreted
and that (Te + Ti)
scale
height Hi,
but more
HN frOm satellite
for the scale
(b) sometimes
the
often they do not, and
36-4i
drag ObseyvatiOns
height of the neutral
particles
,,0
~
/
8ACK,CATT,.
SUMMER 0,,
[1000 -1400 ESTl
I ,0 -
:
B. -
(0900 -1500 EST1
;
g
%
Y
;
,.
.
A ARDC ((959) MODEL ATMOSPHERE
o KALLMAN-BldL (1961. )
. ,,,,...BIJL [(961 b)
4, –
0
KING-HFLE
,
.
dACCHIA (19601
YONEZAWA [89601
110$.19601
t
2.
o
1
(
..0
I
20.
+0.
“,,.”,
800
100
[km)
Fig. 28.
The midday summer and winter values for the scale height of the neutral particles HN obtained from the backscatter values of N by assuming HN = Hi/2,
twether
with satel I ite drag values for H N accors.g
to v~rio.s authOrs. 36-41
32
—-,;
—
,—,-
TABLE V
THE RATIO OF THE NUMBER OF ELECTRONS
ABOVE Nmax TO THE NUMBER BELOW nh
(Mnter
Day Observations)
Date
(1960)
fime
1B Mar
1400-
2 NOV
2 Dec
1
15 Dac
n
a
Ratio “a: “b
(EST)
1.93
I 550
1550-1605
2.30
1422-1455
2.20
1529-1550
1.90
19 Dec
1621-1625
1.97
20 De.
1002-1110
1.64
21 Dec
1628-1653
2.o5
21 De.
1653-1713
2.06
29 De.
1114-1132
I .32
30 De.
1429-1451
1.91
Mean =1 .93+0.26
obtained by various
authors
are compared
tained from the backscatter
height of tbe ionizable
that the summer
seen
4, The Total
Values
Electron
curves
Content
of techniques.
profiles
technique.
obtained
These
the scale
Hi.
It can be
of the Ionosphere
their
measurements
at Jodrell
results
shown in Fig. Z2 were
That is,
ob-
most of the other observations.
have been obtained
values
yielded
nb.
an average
daytime
pub-
of 1959,42 by means
ratio
and the “al”es
workers
for the ratio
The most recently
Bank during the winter
used for comparison
by several
have been obtained
na above Nmax to the number below
for this ratio were
of the moon-echo
bracket
Te = Ti.
constituent
to be half that of the ionization
content of the ionosphere
From
the number of electrons
lished values
winter
and winter
beigbt of the ionizable
by using Eq. (3) and assuming
has been assumed
for the total electron
using a variety
between
results
constituent
with the scale
of about 3:%.
listed
i“ Table
Tbe
V for
were obtained,
These values were obtained by plotti”g the density asa linear f”nctionof
‘a:nb
height and extrapolating
the profile both above md below Nmax.
Below Nmax, the small amount
of ,Iecessary
curve
extrapolation
can be performed
of Fig, ’4(b) obtained
on i8 March.
800 km, beyond which it was assumed
ionization
abo”e
800km constituted
with a fair degree
Abo”e
Nmax,
to decay with a constant
aho”t 10 percent
The mean value of the ratio na:nb obtained
lower
than that obtained
cauae~,
at Jodrell
whenobtained
Bank,
fromionosonde
scale
density
by following
the
was extrapolated
height of Hi = i50km.
to
The
of “a.
in this way is about 2 to 1, which is significantly
It is possible
data,
of confidence
the electron
that the moon-echo
istoolow?i22
However,
result
istoo
high be-
Seddon43 doubts this
explanation
ments.
since his studies indicate good agreement between rocket and ionosonde measure44
Taylor
has suggested that the oblique path of the rays through the ionosphere in the
moon-echo
work may int~od”ce
in the electron
erroneous
“al”es
content as a function of latitude.
ments of na:nb at Trinidad
in the ratio na:nb if there
Millman
(iia N) and found daytime
ratios
are marked
and Rose 45 have reported
lying between
f:i
and 2:i,
variations
measureIt seems
33
..—.—
—
probable,
results
therefore,
obtained
that this ,-atio may be a funct~on of latitude,
at Millstone
(42” N) with those at Jodrell
so that a comparison
Bank (54-N)
or Trinidad
of the
(ii”
N) would
be improper.
111. SPECTRUM
A.
MEASUREMENTS
Introduction
.4 measurement
of the spectral
least as much informational
the shape of the spectrum
Te:Ti.
This dependence
distribution
a measurement
depends
of the energy
of the electron
upon the ratio
in the reflected
density
of electron
is sho\vn in Fig. 29, ~vhere curves
Fig. 29.
signal
profile.
temperature
at
to ion temperature,
obtained by Fejer6
The theoretical
contains
This is true because
for thedlstribution
power spectra camputedby
Feier6f0r
different ”values0f
the ratio
electr~n and i.” temperatures Te: Ti.
between
the
i
,
of echo power
with frequency
that the spectra
case where
therefore
shift
for different
are double-sided
is applicable
L is considerably
to the results
by multiplying
reported
singly charged,
greater
Other assumptions
k equals
is valid for the
length AD [Eq. (2)],
The abscissa
A and a term
used in the derivation
(b) only one type of ion is present,
This figure
than the Debye
in this paper.
of the ions,
It should be made clear
are reproduced.
by the radio wavelength
sound for the ions where mi equals mass
ion temperature.
Te:Ti
.#ith only one half shown in Fig. 29.
the radio wavelength
f normalized
ratios
in Fig.29
related
Boltzmann’s
is the Doppler
to the velocity
constant
of
and Ti equals
of Fig. Z9 are (a) all the atoms
(c) cO1lisiOns are i~requent
and
are
and maY be
neglected and (d) the ray path is not inclined at an angle to the magnetic field lines >85”.
~agneti. field effects,
i.e.. the remOval Of restricseveral ~uthor~7>9,i~ ha”e inve~tigat~d
tion (d), and Pineoand
Hynek
46
have reported
Pineo and Hynek found good qualitative
computed
field
by Renau,
lines.
In order
of a high-power
to achieve
Camnitz
system
a ray pathat
F-region).
Hence,
considered
the effect
this investigation,
on Trinidad.
right angles
between
of the removal
mixtures
current
that at most F-region
of oxygen and helium
Pineo
field
made here,
of restriction
atoms.
investigation
their
results
inclinations
of these effects.
andtbeoretical
between
and Hynek were
It is not possible
to the magnetic
for any measurements
for different
“iew
agreement
and Flood 47 for different
to perform
radar
an experimental
compelled
by use of the Millstone
lines
restriction
(d) is observed.
curves
and the
to make use
Hill
above a height of 100km
(b) and presented
This choice
spectra
the raypath
radar
(in the
Fejer6
has
showing the spectra
waspresumably
dictated
bytbe
heights
0+ is tbe princ iPal ion. The theoretical
argume!lts
48
for this “iewpoint have been summarized
by Rishbeth,
and satellite-borne
mass-spectrometer
50
49
measurements
which cotiirm
this result have been reported by Poloskov
and Istomin.
34
—-.
.... . .
.
has armed
Nic.let5’
1000km
altitude)
evidence
that the outermost
consists
in tbe form
Wallops
Island,
of a helium
of an electron
Virginia)
can be obtained
of helium
ions would be insufficient
filled,
density
which suppotis
t,rements
therefore,
part of the eafl:~
layer,
PrOfile
to 1600km
this view.
we should expect,
to influence
On the basis of the available
and Weekes54
trons is approximately
frequency
ikcps
(c) will be fulfilled.
particles
time.
(most
collisions
to the radio
The presence
However,
heights
atoms to predominate
by two or more
by a large
charged
and ion t:~peratures
Spencer,
rise,
Also,
mperature
which would indicate
evidence
This
electron
and ion temperatures
to the experimental
there
is contrary
prevails
nominally
Ilkcps.
performed
by Pineo
is replaced
repeatedly
frequency
spectrum
to obtain a curve
containing,
say,
that any changes
of the electron
spectmm
obtained in this way.
spectrum
analyzer.
B.
The NW
Spectrum
The rebuilding
number of cqstal
filter
(i. e.,
filters
approximately
ha”e center
Thetwenty-four
intervals
frequency
and permitted
singly
condition
of the elec-
measurements
the volt-ampere
cross
section
of
curves
decreases
the equilibrium
by
that over
of a dumb-
around sun-
conditions
view that equilibrium
are dis -
between
the
(800 -cps)
from
Tbe normal
filter,
the si~al.
and the integration
The electron
each density
profile
Usually
as a function
In order
to overcome
filter,
process
densities
is
corre-
and plotted as a function
about an hourrs time is required
The method suffers
density
receiver
from
of time will
the obvious
disadvantage
show up as a distotiion
of the
this problem,
the author constructed
+962 provided
an opportunity
a
Analyzer
filters.
Hill radar
These
Gaussian)
frequencies
filters
from
a spect mm.
6 points.
of the Millstone
large
at
most parts of the ionosphere
(Johnson 57) and
58
qQ.
using Explorer VIII.
Clearly,
is tuned across
to yield
Hill have been reportecl
measurements.
29
was as follows.
by a narrow-band
of the filter
question
the number of charged
by Serbu,
sponding to a given height are then selected
of tbe offset
Since this
that condition
anopen
exceeds
by the rocket
accepted
throughout
and Hynek
as this filter
of the elec-
patiicles).
to assume
The nonequilibri”m
that the electron
repofled
is much to be gained by further
frequency
tbe shape of the spectra
is supported
to the generally
measurements
The method employed
from
that, at least over this period,
turbed.
It fOl-
of magnitude, we might expect
could be Inferred
has reported
Bowles
(b) will be ful-
iO-23 grams).
ions remains
particles
at Millstone
but at night Te - Ti.
in the daytime
In which:;
~~.
bell probe.
number
margin.
Spectral measurements
of the signals observed
~ineo
et ~ii3,15, z9
Pineo and Hynek29 conclude
most parts of the day Te - 2Ti,
mess
Ti.
it is appropriate
orders
from
the expected
that condition
(mi = 2.675x
being with other charged
of doubly ortriply
fired
spectrum
For these observations,
heights the collision
frequency,
pre,e”t
by a rocket
600 km, where
evidence,
since the number of neutral
at most F-region
charged
that at F-region
approximately
equipment,
shape.
may be LIsed to determine
suggest
is so low compared
the present
(obtained
the spectral
and that the mass of the ion mi will be that of oxygen
Ratcliffe
(beyond
With the present
Only UP to a height of approximately
10WS that the width of the spectrum
tron
atmosphere
and Bauer and Jackson53
and Bauer,
selected
filters
ha”e a response
and a bandwidth between
in the “icinity
of 200kcps,
spanned the range from
tbe upper sideband
range of Oto 42kcps.
during
The filters
half-power
200 to 2i2kcps
bya
signals
points of 460cPs.
Tbe
intervals.
at approximately
to be examined
gatedamplifier
a
that of a single-pole
but are spaced at i60-cps
of the reflected
aredriven
resembling
to acquire
over
500-cPs
a Doppler
(Fig. 30), wbich selects
a
M*, N
RECE(VER
,FAM,L, F,ER
200 * 25,.,,
ti
dL
.
l}.
/{
fig.
from
30.
the time base a region
an amplifier
capable
icon diodes
almost
square-law
devices. )
ranged in a Miller
gration
period
circuit
duced by drifts
orDC
signal
circuits
from
the detectors
were
measurement,
because
Tbe filters
that the mean of the ratios
presumed
that the gain (or the ambient
changed between
mns (the duration
then be scaled
by some constant factor
In this way a spectmm
utes,
which does not suffer
Unfortunately,
range of different
imately
C.
heights,
Results
a period
0n4days
of Observations
earlyin
were
of these measurements
presented
i962 (i5to
made over
containing
any of the ambi~ities
is measured
No attempt was made
of approximately
of signal
energy,
noise alone.
no
Ra-
only noise during either
*6kcps
should be 1:1.
wide:
All the points may
for the last 8 (or SO) fil-
24 points is obtained
height.
It follows,
If not, it can be
ahead of the gated stage has
observed
that arise
only at a single
inteintro-
squared to yield the signal-to-noise
sample
of the receiver
to bring the mean ratio
two hours at night when the signals
obsewations
results
from
the spectrum
(Fig. 30).
USA 4JX) ar-
a 5-minute
on background
is only approximately
measurement
as
of the time base at a range where
repeated
for these filters
noise level)
by
are sil-
behave
the voltage
O.i volt).
of each mn is timed to within +msec).
tersto
unity.
observed
During
each measurement
8 to 12kcps
at 440 McPs the spectmm
therefore,
hours.
which are nefi
in the region
(Philbrick
and far exceed
(approximately
after
signals,
by integrators
DC amplifier
60 volts
is followed
The detectors
to make and match twenty-four
are summed
to place the gated portion
and the measurements
at each frequency.
Each filter
by tbe6e large
feasible
Instead,
tios are then taken of each of the two voltages,
ratio
interval.
constant of several
in the DC amplifiers
adjusted
could be expected.
analyzer
when driven
build up to approximately
of fsets
were
.
.
.
of a chopper-stabilized
to match the gains of each of the 24 channels.
the timing
.
.
.
of the newspectr.1
which,
with a self-time
the voltages
.
.
.
(It was not considered
The currents
consists
.
.
toativenheight
circuit,
detectors.
circuit
.
.
a *i OO-volt peak signal to the detector.
half-wave
linear
Each integrator
corresponding
of delivering
in a simple
identical
B1.ckdiagram
.
.
in 5 or iOmin-
from use of the earlier
In order
i hour is required
method.
to obtain spectra
at a
during the day and approx-
are much weaker.
in 1962
i6 Febma~,
a complete
in this report
i3to
24-hour
is warranted
i4 and 26t027
period.
March
The inclusion
by their bearing
and 4 to2
April)
of some of the results
on the interpretation
in Sec. 11.
36
--,.-
of the
The compromise
complicated
spectral
Sucha
during
between
spectral
range resolution
measurements
width of the transmissions.
For most measurements
pulse would add approximately
for some measurements
for better
frequency
and echo intensity
or +0 percent,
500cPs,
a pl!lse len@hof2msec
In order
resolution.
discussed
in Sec.11 is further
by the need for a long pulse in order
combined
to achieve
to minimize
a pulse length of Imsec
to the half -width
with a very
a reasonable
was chosen.
of the signals,
low ele”ation
degree
the
but
(9”) was used
of range resoltltion,
all
,ncasllrements
were made at elevatiOn angles Of 50” Or leSs, in contrast to those of Pine. and
29
who took the measurements
in the zenith.
A point was chosen on the surface of the esrth
lIyllek,
i,, the vicinity
to different
of iUashin@on,
heights
,nise between
D. C.,
vertically
range resolution,
Ininate different
point.
frequency
height intervals.
of 200, 300, 400,
a 15-minute
plete sequence
of heights
FiWre
3i presents
ing the period
period
i to 2 April.
were
made at ranges
to provide
of +5psec.
was changed,
Measurements
corresponding
about the best comproin order
to illu-
and the gated portion
of the
were
Thus,
made at ranges
corre-
500, 600 a,ld 700 km, thollgh on most days only 400 and
examined.
of integration
could then he examined
a series
seemed
resoltlt ion and signal intensity.
600km or 500 and 700km of the last four were
~veak at night,
This
the antenna elevation
time base was adjusted to an accuracy
spo,?ding to heights
and all the measurements
above’!this
of spectra
only once eveq
corresponding
(The actual region
Because
was employed
illuminated
the signals
are exceedingly
for most observations.
The com -
2 hours.
to a height of 300km and obtai,led
by the pulse was from
d“r-
265 to 335 km.)
Fig. 31.
Spectra Obtained fOrincOheren+ backscatfer
signals at o delay corresponding tO 300 km height,
1 t02 April 1962.
—..—
LOCAL
TIME
LOCAL TIME
{EST1
(EsT)
(b)
(.)
!
!
,’!
LOCAL
TIME
{EST)
LOCAL
TIME
(EST]
(d)
(c)
Fig. 32(a-e).
The half-bandwidthof
the signals
observed at a delay corresponding to. height of
(.)200
km, (b)300 km, (c)400
km, (d)500km
and (e) 600 and 700 km.
LOCAL
(e)
38
TIME
(EST)
These
results
were
gate width.
Obtained by using $-msec
Although
and transmitter
the intensity
is first
These
These
spoiled
and are presented
time (2200-0300
EST)
and daytime
are shown in Fig. 33.
The vertical
height interval
together
during either
occupied
in Fig. 32(e).
(0900-1500
EST)
values
bars, associated
whereas
Ti and this region
that the electron
the receiver
bandwidth were
spectra
in the range
and an IBM 7090 digital
h is ten times
tained.
Fi~re
center
frequency
perature
of the signals
but
of the fi-
The values
obtained
obtainable
at
measurements
run.
cumes
bars indicate
does not vary
wel.e
The average
night-
for the bandwidth as a function
of height
represent
the rms scatter
rapidly
the
of the
with height.
This
above 300 km are not in systematic
Such an error
than the si~al
width varied
(Fig. 3i) to determine
computer
presented
because
er -
could occur
if
then the energy
with height.
o~gen
increases
of the ion temperature
to calculate
of the echo power
of the ratio Te:Ti.
obtained
we$e
being indistin@ishable
two additional
In Fig. 36 the position
Te :Ti,
cumes
are obat the
the tem-
of the half-power
point
It can be seen that the bandwidth
Thus,
if the spectral
shown in Fig, 32(a-e)
of Ti alone,
The spectra
and that the radio wave-
curve has been used to determine
ratio increases.
of the signal bandwidth
terp~et ed as being caused by a variation
ratio
of Group 33
the spectra
at the peak of the wing to the power
This
data as in Fig. 3 i.
of the temperature
as the temperature
(the curves
in Fig. 34, from wtich
T<,
temperature
by DF. M. Loewenthal
was employed
is the only ion present
length ~
and are presented
experimental
known, tbe variation
by Fejer3
values
of the electron-to-ion
was used to make the actual computations.
that atomic
the value of the Debye
as a function
for values
This work was undertaken
The theory
as a function
ratio f?om
because
of the results
of height.
as or narrower
have been computed
35 shows the ratio
has been plotted
profiles
as a function
if the spectral
1.0 to 4.0.
on the assumption
from those for L/hD = ‘),
well
as narrow
to make use of the spectra
at the author 1s request.
length
pulses
are not precise
Values
of theoretical
calculated
density
bandwidth changes
in the pass band would vaw
ratio Te:Ti
using i-msec
factors
since the bandwidth is proportional
to the square root of the ion tem34
However,
these experimental
results
tbe signal
In order
The half-power
is thought to be isothermal.
ror because
a series
obtained
calibration
the horizontal
is to be expected,
Temperature
way.
in the wing of the curve,
with the points in these
perature
D.
of
variation
shape.
Some of the spectral
behavior
density
diurnal
in the following
respectively.
or the noise
It will be noted that above 300 km the bandwidth
the supposition
of
width of the spectra
32(a-e),
“al”es.
confirm
noise fi~re
diurnal variation
in the spectmm
of the poor quality
the signal
by the pulse,
receiver
for the bandwidth obtained in this way at 200, 300,
few in number because
by interference
is also a clear
correction
for the increased
400, 500, 600 and 700 km height are shown in Figs.
these heights,
of tbe receiver
is a clear
by 500 CP8 for curves
The values
with a i-msec
is half the value observed
emplOyed.
correchon
width of the pulses.
at 600 and 700 km were
there
changes
has been measured
aye reduced
pulses were
to make a first-order
nite spectral
imPortant,
at which the power
values
2-msec
ratiO is a function
tOgether with small
of each of the spectra
extracted.
and 250 CPS where
serve
What is more
taken as the frequency
pulses together
Of which is whOlly stable — there
width of the signals,
The bandwidth
point,
the absOlute signal-tO-nOise
power — neither
of the siqals.
the spectral
transmitter
the ratio Te :Ti,
shape is nOt
cannot be accurately
or a combination
in-
of these
effects.
The shapes of the spectra
~e~i,
i .e,,
equilibrium
re suit of equal increases
are well-defined
prevails.
Thus,
in the electron
for 200 km height ad
the small
indicate
bandwidth variation
and io” temperatures
that at all times
seen in Fig. 3Z(a) is the
during the daytime.
——
.
———
600
500
~
=
+00
g
g
,0.
,00
T
I ..,,, ME 0,00.1500 EST
I N,GHTT, ME 2200-0~ EST
HORIZONTAL BARS DENOTE ‘-
,.s
oE”ILTION
VERTICAL BARS INDICATE
THE “El.”,
INTERVAL
OCC” PIED BY THE PULSE
;
~
+fl
,
-~.
/:
;
~
/
Fig, 33,
The overage half-bandwidth
of the signals plotted
as a function Of height for nighttime (2200-0300
EST) and
daytime (0900-1 500 EST) obsewations.
+
+
,4
6
4
HALF BANWIDTH
(KCP$I
Fig. 34.
The power spectra predicted
by the theory given by Feier6
for .Ie.tr.”-to-io”
temperature ratios in the range T.: Ti = 1.0 to 4.0.
(These curves were computed by Dr. M. Loewenthal.)
~
4,.
~
,,
g
&
t
?
fig. 35. The ratio of the echo ~wer
center frequency plotted as a function
obtained from Fig. 34.
in the “wing” to that at the
of Te: Ti. These pints were
y
30
>
$
k
B
% 22 2
,. ,.4
1~
,.,
,.8
Te:,,
40
The values
for the power
are shown in Fig. 37.
ii:
i exists
clear
the value increases
is vew
possible
It seems
between
large,
to decide
roughly
because
whether
the wing and center
that at both these heights
during the hours of darkness,
the daytime
“alues
ratio
indicating
the diurnal
at 300 a“d 400 km
ratio
(Te = Ti)
observed
to make.
of approximately
35,
as in Fig.
to the sun’s altitude,
is difficult
variation
a power
equilibrium
in proportion
this measurement
observed
During
but the scatter
Therefore,
at 400 km is greater
of the
it seems
im-
or less than that
at 300 km.
At 300 km the quality
a 2-msec
evation
pulse at a vev
(22.5”).
and a weighted
elevation
low
according
mean computed
shown are the weighted
partly
reflect
different
(9”) and others
ratios
Te:Ti
noon, possibly
near iOOO EST.
ond source
of atmospheric
heating
sufficiently
precise
iation shown in Fig. 38 will
Thus,
we are faced with various
1 to 2 April),
shows the “al”es
to the power
ratios
between
to reject
plotted
since the collision
along the
the temperatures
that the peak occurs
at noon, and that the variation
It seems
likely
and with the solar
is not sufficient Iy well
the results
defined to dete?mine
to obtain values
of which the following
that the diurnal
for the daytime
represent
that abo”e
at 400 km are at least as large
trend can onlyco”tinue
for a limited
phere also decreases
with height.
The temperature
distributions
Of the two hypotheses,
drag results,
to take place
of the similar
a large
for a
two etiremes:
well with the variation
wavelength
the solar
of the temperatu~e
particle
solar
km does not seem to be isothe~mal,
energy
flux
S
(i)
choice
of the neutral
to
m 100
and (2) are shown in
particles
as these authors
satellite
TN is known
that TN = Ti because
Ti shown in Fig. 39
in the model developed
60
150
units,
to
this
by tbe atmos-
since, from
The temperatures
assumed
of
declines
However,
absorbed
(It can be presumed
s.)
rapidly
as those at 300 km.
than decrease.
to the two hypotheses
of 500 to 700 km.
anything
tempera-
we might expect the time it takes the
rather
for (2) seem tbe better
of the ions and neutral
10.7-cm
because
co~responding
diu~nal “a~iatio”
for a height of 300 km agree
and Priester
with height,
distance
the curves
at heights in the order
masses
decreases
300 km the ratio Te:Ti
with the ions to increase
var-
sunspot cycle.
a third possibility
frequency
exists
might be taken as evidence in favor of the sec59
Yet, the results are not
and Priester.
of Te:Ti
to reach equilibrium
for the
by Harris
possibilities,
observed
The er-
and must
Abo”e 300 km the ratio Te: Ti may be constant (and follow tbe variation at
300 km), with the increase in bandwidth caused by an increase in Ti (and
a corresponding
increase in Te).
Also,
300
frequency),
are shown in Fig. 38.
of the points is quite large
in the ratio
el-
each of the spec-
(2)
8ince the ratios
abo”e
from
at the center
Above 300 km, Ti may be constant with height, the increase in the bandwidth of the signals being caused solely by an increase in the ratio Te:Ti.
It is possible
Fig. 39.
by “sing
(i)
unity,
electrons
obtained
axis of this fi@re
change both with season
in interpreting
obtained
pulse at a much higher
(measured
to the sun’s altitude.
400 km the shape of the profiles
but the bandwidth.
ture,
This
the possibility
proportional
ratios
mean “alues
corresponding
suggested
were
days (i3 to 44 and 26 to 27 March,
that maximum
just before
spectra
ratio
The right-hand
It would appear
to exclude
power
The scatter
on the three
in Fig. 38.
during the day is directly
some
with a l-msec
These
for each hour.
rms deviations.
temperature
left -hand ordinate.
Abo”e
because
to the signal-to-noise
conditions
which have been included
electron-to-ion
varies
The value S fOr the W$ng-to-center
tra have been weighted
rors
of the spectra
However,
by Harris
the
region
suppose.
1
-—,.”..——
A
.J
2.2
30
Fig. 36.
The position of the “half-bandwidth”
~,.
function of Te: Ti (ObfOined frOm Fig. 34).
point
~~~~
~~
38
7C :,,
.0
H
L
:
2,,
.
z
0
K
*
:
Fig. 37.
The observed values for the ratio of the
echo power in the “wing” to that at the center
frequency for 300 and 400 km height intervals.
0
,.,
,
~
z
.
.0
00
r
000(
,;ol”m;.<
,,0,,0,
,.o~””.;l
0600
,200
LOCALTIME(EST)
}
I’ei
Fig. 38.
The rms vol”es for the points given in Fig.37 for
each hourly interval.
Shown on the right-hand
ordinate
is the corresponding scale that gives the ratio betieen
the
electro” a“d ion temperatures.
NIGHT [2200-0300
,00
-
~ =,
“
600 w
DAY (0900-1500
es,]
EST]
T(C,)
l’”
‘L
,\/
‘s
/’
:
~
;’!+
,/’
*,,*
E
Fig, 39. The temperatures derived from the results
of spectrum measurement (e. g., fig. 31), by means
of the curves given in Figs. 35 and 36.
The two
daytime curves represent
the extremes of possible
behavior caused by the inabili~
tO determine te:Ti
for al tit.de$ >400 km.
s
w ,00
x
“i’
-$
,00 ~
o
+’
~j,
.
,2
~------”’”
,000
..00
,,00
K(NETIC TEMPERATURE
(°K1
42
I
,
,,
~
The large
difference
between
the att;6mpts of variOus wOrkers
Bauer
and Eva”s16)
by assuming
to determine
Te = Ti.
ation reported
Spencer,
G %.
the atmospheric
feature
of the Spectrum
of +70 to Z30 km.
Somewhat
extent of the nonequilibrium
of values
was any more
and midnight
from
of the new results
are in equilibrium
higher,
in the region
condition
represented
or less pronounced
and ion temperatures
would still
temperature
electron
density
profiles
seems
to be the di”~nal
varia-
Measurements
takes place in the daytime.
wide scatter
300 km invalidates
23
Jackson a“d
shown in Fig. 38.
The elect ron and ion temperatuhs
equilibrium
above
Hanson and McKibbi”,
the results demonstrate
the existence of tbe large diurnal vari58
together
with
the
nonequilibrium
conditions first reported by
G g.,
by Serbu,
55
The most important
Summary
and ion t:~peratures
Instead,
tion of the ratio Te:Ti
E.
the electron
(Van Zandt and Bowles,
appeared
temperatures
at all times
265 to 335 km,
Evidently,
could be determined
Te and Ti,
re~on
to decide
The greatest
near noon when Te:Ti
from
The values
that their
ratio
The
heights.
whether
ratio between
= i.6,
computed. on the assumption
hold at 600 to 700 km, are given in Table
depatiure
is quite small,
at only 300- and 400-km
it impossible
at 400 than at 300 km.
to occur
the height inte?”al
a pronounced
the transition
by the points makes
over
The
the effect
the electron
for the midday
at
300
km
VI.
TA8LE VI
I
I
IV.
TEMPERATURES
ABSOLUTE
A.
I
H;ig;t
I
Ti = Te (night)
‘K
I
Ti (day)
“K
T, (day)
‘K
200
686*18
300
775 &48
1230 +41
I 770*59
1840+93
920 f 83
92o i 83
400
866 *43
1280 +64
500
838 + ?
I 450*90
2080 * 130
600/700
1000 *IIO
1530+110
221 O+I7O
SCATTE~G
CROSS
SECTION
OF THE
ELECTRONS
section
of the electrons
Introduction
Gordon’
give
a value for the scattering
‘e=(~jz
and this is the cross
= 4noe,
Various
section
normalized
theoretical
workers
place
from
as
(4)
to unit solid angle.
Thus, the radar cross section
3,6-ii
soon showed that, where measurements
are con-
and on the assumption
Um would be only half this value.
Of as ttiing
cross
i“Gaussian””its,
‘m
ducted at Iong wavelengths
sphere,
DERIVED FROM THE SPECTRUM MEASUREMENTS
ACCORDING
TO HYPOTHESIS
(2)
individual
by the motion of the ions.
electrons
that thermal
This is tme
but from
Under these conditions
because
their
equilibrium
collective
the expected
prevails
the scattering
in the iono-
cannot be tbo”ght
disturbed
behavior caused
56
value for cm becomes
(5)
I
——
. ...”.
.
The observed
Te:Ti,
cross
section will,
as can be inferred
from
Buneman 27 has discussed
however,
the variation
depend on the electron-to-ion
of the area under the curves
this aspect of the problem
ation of u~ as a function of Te:Ti
obtained
from
in some detail,
temperature
in Figs.29
and Fig.40
ratio
and 34.
shows the vari-
his paper.
m
~
e“,
80
i
~s
:
y
g4
5
g
:
Fig. 40.
The theoretical variation of the scattering
cross section of an electron as.
function of Te:Ti
(after Buneman27).
*
O.
02
,.7,0OF
In an early
05
1.
ELECTRONT~,:N
paper
PineO,
dar cross
seCtiOn Um observed
Gordon.i
This was later
Om
!IIJ
50
ZO
& ~., ‘3 ga”e the misleading
at Millstone
corrected
=,.4
100
TEMPERATURE
x io-29
impression
that the value for the ra-
Radar was in good agreement
by Pineo
and Briscoe
with the value
in Ref. 14, where
given by
a value
(6)
mz
was published.
Bowles56
“ided
has devoted
considerable
attention
to the measurement
Of the cross
Se CtiOn.
Pro-
that a loss between
Bowles
obtains values
value in Eq. (5).
0.5 and 1.0 db can be attributed to absorption in the lower ionosphere,
for the cross section Um which are in good agreement with the theoretical
In addition,
& a., and the parameters
tially
better
evant,
agreement
therefore,
he took values
of tbe Millstone
for the echo power
radar
up this discrepancy
at Millstone
and Obtained a value Cm = 3.6.
with Eq. (5) than that fOund by Pineo,
to clear
observed
before
~~,
proceeding
‘n Eq( 6)’
further
by Pineo,
This ‘n substan‘t wOuld ‘eem
with the derivation
‘elof a
new value for um.
B.
The %dar
Quation
Bowles 56 has discussed
backscatter
takes.
measurements.
In Eq. (6) of his report
for an Extended
Target
at length the derivation
His account is excellent
the equation
of the radar
in its detail,
for the received
equation
applicable
but seems
echo power
Pr
to incoherent
to contain some misis
44
——.
-
. ——-—-—
.-—
where
the symbols
used by Bowles
are:
Pt = peak transmitted
power
(assumed
Vr = efficiency
of the feeder sYstem
antenna and feed wires),
c = total CFOSS section
constant within the pulse)
(i. e.,
per unit “Ol”me
over-all
resistive
in watts,
losses
in the
(m3)
= Nom.
In these
symbols
N = number of electrons/m3
. 1.z4f:
fo=
x 10‘o,. ~here
critical
= cross
‘m
~ = velocity
frequency
section
in Mcps;
of an electron
of light (approx.
, = pulselength
volume;
= gain of the antenna over
angles @ and q, where
e = angle measured
q = azimuth
Bowles’
3 X 108 m/see);
(see);
R = range to the scattering
G(ep)
from
a lossless
ume within a given incremental
because
isotropic
the axis of the principal
angle of the direction
Eq. (6) is in error
radiator
at
lobe,
of the ray,
he has stated
(Ref. 56, P. 25) that the total scattering
vol-
solid angle is
de d@
2
CTR2
In the coordinate
(Fig. 45);
system
(7)
adopted by Bowles,
Eq. (7) should be
(8)
Thus,
Bowles’
Eq. (6) should have been stated as’”
(9)
For antennas like that employed
radiation
pattern,
at Millstone
Eq. (9) now becomes
Pr
= =
~
Radar,
(by integrating
.z(~}
sine
which has a spherically
q over
symmetrical
O to 2n)
(io)
de
e
Equation
a power
tance
(!0)
can be developed
Pt driving
an isotropic
R the flux density
veq
antenna.
simply
as follows.
The total power
Consider
radiated
will
a transmitter
developing
be Ptq ~, and at a dis-
will be
Ptv ~
(Ii)
watts/m2
4nR2
* Note added in p~
The mistake discussed here has since been rectified by the authors.
See K. L. BOW
II:S,
G. R. Ochs and J. L. Green,
“O. the Absolute l“te”sity of Incoherent Scatter Echoes from the Ionosphere,
J. Research Natl. B“r. Standards 6@,
395( 1962).
45
If the antenna is replaced
tern is symmetrical
by one having a gain
G over
an isotropic
about the axis of the main beam,
antenna whose radiation
then in any direction
e from
pat-
this axis the
flux will be
PfqrG(~)
flux =
(i2)
watts/m2
4nR2
brow consider
the annulus shown in Fig. 41.
stated in Eq. (12).
only,
cross
therefore,
volume
If N is the electron
Om.
provided
that c7/2 ~< R,
shown in Fig. 4i and write
density
this elemental
section
across
The area of the annulus is 2nR2 sin e de m2.
having a depth cr/2;
the elemental
The flux density
WE maY neglect
the volume
per m3 and it may be assumed
volume
Where
contains
section
a region
the cOnical nature Of
of the element
that N is slowly
TR2CTN sin Q de electrOns,
Nom = o, the total cross
any part of this annulus is
The pulse illuminates
as R2cr
sin e de m3.
changing with height
each Of which has a scattering
provided
by this elemental
volume
becomes
croes
Combining
watts.
Eqs. (i2)
section
and (i3),
of which a fraction
(watts/m2)
= nR2CT0 sine
is scattered
(13)
m2
we have for the total intercepted
is given by the product
.,,.
de
back to the transmitting
of Eq. (13) and (4mR2)”i.
power
0.25 PtqrG(e)
CTU sine
de
antenna where the flux density
The flux which falls
within the antenna
,.1s
OF ANTENNA
,,8
41. An elemental ann.1.s lying
disto”.e
R from the observer.
R
46
i“
the ionosphere
aperture
tive)
is (partly)
collected
and conveyed
area of the antenna for radiation
Aeff(e)
The resistive
elemental
losses
volume
to the antenna terminals.
at an angle
e may be written
The collecting
as Aeff( e),
[or effec-
where
= ~
(i4)
will be present
can be written
during this process
Ptq~CTCG(e)
power
so that the received
power
from
this
3s
Aeff(~)
sin e de
=
watts
(45)
16TR2
If we now consider
all the possible
power
is
Pr obtained
—1
=
G(0)
i6mR2
By substituting
volumes
corresponding
to all
e,
the total ?ecei”ed
7/2
ptv:CTU
Pr
\
elemental
Aeff(e)
sine
de
de
watts
watts
(i6)
,
(47)
e
Eq. (14) into (16) it becomes
P,=
‘~4~~~a2
~n’2
G’(e)
sine
e
which is clearly
C.
the same as Eq. (i O).
Approximate
%dar
In Sec. B we developed
etiended
rive
target
illuminated
an approximate
the approximate
In Eq. (i7)
Equation
a general
let G(e)
energy
The Millstone
falling
radiation
pattern
Gaussian
f“nctio”;
for the radar
symmetrical
equation to be employed
antenna.
In this section
for an anten~6 of the type used at Millstone
i4
and Pineo ad Hynek,
be replaced
aperture
on the edges
Antenna
for an
we shall de-
and compare
it with
used by Bowles
ured along tbe axis ( e = O) and F(e)
angles.
expression
by a spherically
expression
expressions
for a Millstone-Type
by Ge=OF(e),
where
Ge=o
is the gain of the mtenna
is unity at 6 = O and specifies
has a tapered
feed distribution
bow the gain falls
(approximately
of the dish from the horn is about one-tenth
of this antenna is such that the main lobe cm be closely
meas-
off at other
Gaussian)
and the
of that in the center.
rep~esented
The
by a
hence we shall write
F(e)
= exp[–o.7e2/ef,2]
is the half beamwidth,
‘here
e i/2
gral in Eq. (i7) becomes
(i8)
,
i.e.,
the value for
e for which F(e)
= i/2.
Thus,
the inte-
(i9)
By making the transformation
r = R6 for small
e,
Eq. (19) becomes
(20)
This is the familiar
~orn~ eXP [–a2X2]
integral
dx whose
solution
is I = i/2a2.
TherefOre,
Eq. (20)
yields
(2i)
For this type of antenna,::
Goc~
(22)
,
a
where
A is the physical
aperture.
qA = Aef~A
Thus,
if we define
(23)
>
for this antema
(24)
qA = 7/4r
AISO,
the beamwidtht
is
(25)
-~
2el/2
where
Eq. (2i)
D = diameter.
- 57D
,
If Eq. (22) is written
as
becomes
I-GO
7TD2
~
2,8 x4k
(26)
=)2
‘ii4D
(27)
s0.74Go
Actual
substitution
in Eq. (2i)
of the measured
yields
I = 0.76 Go.
Therefore,
values
for ei,z
0.76
antenna’
Eq. (17) becomes
Ptq; cTua2
Pr=
and Go of the Millstone
64=2R2
Go
watts
,
(28)
or
Ptq;
cruAo
(29)
watt s
PF = 0.76
i6nR2
* Reference
Data for Radio Engineers,
p. 700.
t Ibid.
48
Pineo
ha”e used this equation without the factor
and Hyneki4
deri”ed
values
by these authors to be a factor
for c m
Bowles56 has considered
wasted.
He defines
the effect
an efficiency
radiated.
factor.
which is radiated
Power
upper limit
Thus,
Bowles$ term
q:
his approximate
at some angle
does not form
Of the integral
radiated
of the power
Eq. (29) contains
e > emax
a hemisphere
hence,
we should expect
into the sidelohes,
q ~ as being the ratio
factor
t}le total power
since the ionosphere
of power
0.76;
of 0.76 of the true values.
in the main lobe to
a term q:
may rightly
above the obser”er.
sign (x/2) shOuld he replaced
which is largely
to account for this
be regarded
as wasted
Therefore,
i“ Eq. (i7)
by sOme lesser
value of emax.
the
Then
would be given by
(30)
This definition
apparently
differs
from
that given by Bowles.
The exact value of Qmax is debat Able.
takes the view that onlY POwer in the main lobe is useful,
antennas such as the one employed
contained
in the side lobes adjacent
no simple
criterion
to dete~mi”e
may be taken as approximately
to the main lobe is not wasted,
can be laid down,
emax
iO to 20” for narrow-beam
the term q~ is warranted
only by the extended
as can he seen in Eq. ( 30) where,
the integrals
-0
and q~ -
opment.
power
Bowles
apparently
is proportional
one actually
i.
measures
It is equally
This
conclusion
believes
the product
if VA is assumed
q A q ~.
to be 0.6 US - 0.58J’
Since q;
labor this point (and indeed the whole
a radio
Bowles
value is nearer
occurs
from
way to measure
in his report*
(the tme
(e.g.,
radar
observadevel-
star) the received
states
that for Millstone,
40 percent),
discussion)
in
the antenna efficiency,
in the final equation,
of the preceding
that
the upper limit to
part of Bowlest
us to the second confusing
Thus,
is 35 percent
emax
NO such term ii-Present
for such a target,
that even for a point target
that
of ma flitude,
true that V8 cannot be determined
brings
(e ~/2 = ~“),
It is evident
It should he made clear
nature of the target.
to T Aq ~A and, since this is a common
where the antenna efficiency
We
but, as an order
antennas.
the case of a point target
tions of a point target.
although for narrow-beam
by him (e ~,z = 1“/2) and the one used by Pineo
the power
BOWle S
11
qAQ~ = 0.35 and
this is a large
because
effect.
the differences
be-
tween the results of Pineo and Bowles center around the term V8 and how it is determined,
Pineo
44
and Hynek
have included no such term in their analysis,
believing that ~~ - $ for a Millstonetype antenna,
so that their
value for Om is about one-third
of the value which Bowles
obtains
from
the same data.
D.
Values
of ~A,
The total two-way
~r and q~ for Millstone
feedline
0.40 for VA can be obttined
losses
given in Table
from the ratio
This value is low compared
sult of attempts
to minimize
a feed system
which protides
This is “ecessa~
net effect
for tracking
is to decrease
to the efficiency
sidelobe
introduced
more than a iO-db taper
operations
qA and increase
I are 2 db,
of the effective
ture (52o m2).
the large
fidar
kt
= 0.63.
A value of
stated in Eq. (24) and arises
by the feed support
stmct”re
illumination
fo~ backscatte~
q~, though the increase
49
q;
(2i0 m2) to the physical
of the prima~y
unnecessary
* POge 35,
Hence,
aperture
as a reby6~sing
pattern.
measurements.
in the latter
aper-
is insufficient
The
to
offset
the decrease
absolute
in VA.
The value fOr the effective
gain measurements
A “alue
[Eq. (14)]
for qa is more
depends upon the square
plots fo~ the Millstone
difficult
and observations
to arrive
at.
of the gain integrated
a“tenns
aperture
given by Fritsch
(Table
of intense
1) is consistent
radio
with bOth
stars.
It will be noted that,
as defined
in Eq. (30),
it
between O and ernax.
Unfortunately,
the cOntOur
62
do not cover a sufficiently
wide range of angles
to permit
q~ to be determined,
Instead, we shall deri”e an approximate
value using results ob63
tained by Ricardi.
R,cardi has shown that if the antenna radiation patte~n is broken into two
parts,
a main lobe and an isotropic
component,
the peak intensity
ratio between
these two can be
found as follows:
gain
the peak of the main beam
isotropic
component
at
-
mG
0
,
(31)
m—i
where
ideal
gain Gi
m = observed
in which the ideal
the Millstone
i3(ei/2)2
~
(33)
antenna the beamwidth
tained from Eq. (33),
is 9544.
m ~ 1.7 in Eq. (32).
Thus,
beam and the average
these numbers
the ratio
sidelohe
J:
‘ax
for the antenna pattern
at Millstone
When the integral
=
by integrating
This
gi”en
600,
by computing
for
the peak of the main
tbe integral
of the new 200-ft parabolic
numerically
for angles
I!,,
=
of
(34)
antenna has a half-power
then
i” < emax
beamwidth
1!.
<90”.
under con-
2e ~,2 = 0.74” (0.0067 radian),
= ia, yielded
to emax
up to emax
i .oooi4
antenna presently
I! = 0,0008243 steradian.
= 4“, a value 1“ = 1.00012 I’ was ob-
Clea?ly,
there is little
It follows
difference
between
that v ~ = 1 and that PineO and
this term.
in Eq. (2i)
numerically
and the ratio between
4i. 3 db. The ratio between the square
2 . . . .
from unity.
that US 1s lndlstln~ishable
de
model
integrated
computed
right to i pore
The result
sine
was re-e”aluated
the integral
Hynek were
F2(e)
Hill,
and when emax
of
i) = 2,4:1,
is approximately
was performed
of a scale
and for this value Eq. (34),
ValUeS
(m/m–
level
is 82.6 db, and this is so large
1=
tained,
2e i/2 = 2.i~ (0.369 radian); hence, the ideal gain, obgain (cOrrespOnding tO 37.5db) is 56z34 which yields
The observed
A check on this conclusion
struction
(32)
,
gain Gi is given as
Gi=
For
gain Go
for the solution
of the integral
over the actual antenna pattern
in Eq. (i7) has alSO :~en
of the Millstone
antenna.
checked
Tbe re suit
obtained,
(35)
is so close to the solution
use for the observations
given in Eq. (2i)
reported
here.
that Eq. (29) can be taken as the correct
Equation
50
(29) may be rewritten
as
equation to
0.76q:Ptc7Aeff(
Pr
1.24 X 10io)
f~rm
=
watts
;
(36)
16nR2
therefore,
0.76q:PtCTAeff(
P,R2
~z
0
BY setting
P= = Pdb,
of the signal,
i.24 x *Oio)
=
where
mks
Pd is the power density
and introducing
the parameters
0.76~:PtC?Aeff(
PdR2b
~2
0
=
bandwidth
An Average
The computer
program
The values
bandwidth.
though the normalized
ter
(38)
(39)
(Fig.
33) during the daytime
is approximately
of values.
2
all the variable
for the electron
obtained
density
these values
qllantities
profile
i4
by 10
on the left-hand
calculates
to Nmax for the profiles
corresponding
Tbe Ft. Belvoir
power
density
values
PdR’
into Eq. (40) yields
for f. were
does increase
for all points
that were
as a four-
-
to five-digit
shown in Sec. 11 have been
made using the %i-kcps
used throughout.
as f:
side of the equation.
tbe value of PdR2 correspo,ld
so that they appear
in Fig. 42 for those measurements
The mean value for PdR2/f~
when inserted
(40)
m
Value for um
plotted as a function of f:
which,
I, Eq. (37) becomes
mks
-18 PdR2
—
~2
o
=i,34xf0
ing to each point and multiplies
receiver
bandwidth
mks
b for most height intervals
In Eq. (39) we have grouped
““mber.
in Table
and b is the effective
Hence,
‘m
E.
(watts/cps)
{6x
m
il kcps.
given
(37)
i.24 X iO1o) Um
= 0,82 ~ ~022a
The effective
Om
16T
increases,
It can be seen that althere
iS a wide SCat-
shown in Fig. 42 is t.35 X iO-4i
-29 ~2,
inks,
a value am - 1.81 X 10
Fig. 42.
The variation
of the product of the p.wer densi ty Pd Of the reflected
signals ond the square of the range
R2 ~, ~ fu.c tie” of the square .f the F2 layer cri tica[ frequency fO. The values for P R2 correspond tO the peak of
the layer and were obtaine $ for al I the profi Ies show” i“
Figs. 3 through 17 where a receiver
bandwidth of I I kcps
had bee” emPIo ed.
The ..1 ues for fO are those obtained
at Ft. Belvoir (B Y.
-—
—.-
—
There
are se”eral
sources
errors
in the estimation
feeder
losses
v, and possibly
of these values
&i db,
Also,
responsible
of error
power
Pt,
are errors
Presumably,
the effective
the method of calibrating
would be approximately
there
in the above value.
of the transmitter
the receiver.
of both Pd and fo.
of the points Jn Fig. 42, although
for the scatter
the next may make a contribution.
Variations
of Te:Ti
are systematic
An outside
*O. 5 db, so that the probable
of measurement
there
antenna aperture
error
limit
the
on each
would be approximately
Undoubtedly
small
Aeff>
changes
these
are partly
in Pt from
must also contribute
somewhat
one run to
to the scat-
ter in the values.
Two systematic
The first
errors
is the error
which act to _
in the profile
with the true distribution.
discltssed
tenna elevation)
N ~ax
error,
ond error
arises
of tbe true value,
used. in the receiver
By convolving
31), one can examine
been chosen to maximize
nal spectmm.
80 percent
value for .m deserve
due to the convolution
which is most serious
the trend of the electron
from the use of an equivalent
of the filter
bandwidth of ii kcps.
Fig.
density
in the vicinity
density
such as that shown in Fig. 3, it can be estimated
may be only 90 percent
tual response
(e.g.,
This
in Sec. 11. By observing
the observed
for the electro,,
the signal-to-noise
The observed
signal-to-noise
of that which would be obtained
in a manner which would cause a-
...
FiWre
but is byno
therefore,
with an ideal
43 shows the ac-
with the actual echo power
ratio,
means a perfect
These
distribution
The filter
appears
filter.
to be underestimated,
at
The sec-
made with a receiver
on the spectrum.
ratio,
an-
density
at i5” elevation.
b in Eq. (38).
curve
of the filter
has been
(actually
that the observed
for all the measurements
this response
the effect
of Nmax,
vs pulselength
even for observations
bandwidth
comment.
of the pulse
bandwidth has
match to the sig-
to be approximately
two systematic
and have a “alue
errors
act
of only 70 + iO percent
of the true value during tbe daytime
Fig. 43.
The response curve for the matched
HI ter employed in the receiver.
Finally,
the basis
of u~ with the temperature
in view of the variation
of the spectmm
look for this it was considered
with the true distribution.
that Um will extibit
measurements,
necessa~
to correct
Accordingly,
the values
the effective
pulse length and the relationship
extrapolated
to yield
pulse.
Tbe correction
we chose values
profiles
“alues
derived
shown in Figs. 4 through
were
scaled
up according
match between
the si~al
used tO provide
values
terval
factors
for the product
PdR2
an ii-kcps
VII,
of the convolution
for Dm by use of Eq. (40).
VIII.
receiver
filter.
of the pulse
against
law could be
VII.
Finally,
values
It can be seen that,
short
For analysis
on each of the
bandwidth was employed.
by a factor
Tbe average
plotted
This
density
on
to
with an exceedingly
are given in Table
to the peak electron
and increased
and the receiver
In order
shown in Fig. 3 were
obtained was found to be linear.
from this relation
18, where
over the day are given in Table
for the effect
for Nmax
corresponding
to Table
spectrum
ratio Te: Ti we might expect.
a diurnal variation.
which might ha”e been observed
the value of Nmax,
“1 I -kcps”
These
1.25 to allow for the mis-
these corrected
values
were
fOr am for each hourly in-
although there
is a elighttendency
52
.—
—
&
CORRECTION
FACTORS
FOR VALUES
900
1.433
60”
I .365
45”
1.274
30°
1.212
20J
I.la
15“
1,116
TABLE Vlll
AVERAGE
Local Time
(E5T)
Me..
VALUES
FOR
c
m
VOI .e OF o
(X IO-29m
Z)m
rms Deviation
07-08
1.57
08-09
2.94
*0.238X
09-10
2.67
*0.99X
10-11
2.72
*0.71
11-}2
3.73
(single ..1”.)
10-29
~z
10-29
~2
x }0-29
~z
(single value)
12-13
13–14
2.72
● 0,35X
10-29
~2
14-15
2,41
*0.42X
10-29
~z
15-16
3.12
● 0,49X
10-29
~2
16-17
3.20
*0.77X
,0-29
~z
17-18
18-19
19-20
3.27
(single value)
TABLE IX
VALUES FOR THE ION
TEMPEMTURE
Ti DEDUCED
THE SCALE HEIGHT MEASUREMENTS
(Sec. 11) ASSUMING
FROM
Writer
(0900 -;;~
True Height
(km)
783
1090
500
980
1320
600
Iloo
I 530
700
I 220
1740
near midday
for this result
(as might be expected),
to be regarded
tend to mask whatever
variation
as conclusive.
may exist.
the rms deviations
Prest,mably
increases
the probable
error,
of the points are too
the large
A weighted- ~9ean vallje
m2.
for the hours 0800 to +700 EST is Om = 2.82 * 0.49 x io
eq~lipment parameters
Ti
Summer Day
(lOOO ~;;~
EST)
Doy
EST)
400
for um to decrease
large
Te = 1.6
experimental
for Cm obtained
errors
from
The *i db uncertainty
so that the final result
Table
1X
as to the
for the average
day-
time value for am is
= 2.8 + 0,8 X iO
‘m
This value is somewhat
Te:Ti
lower
during
1960-61.
the observed
F.
and expected
cross
if the temperature
of 2 or more,
sections
for a maxi,num
value of Vm wOuld be - 4 x +0
could be resolved
ratiO Te:Ti
as suggested
into closer
temperature
ratio
-29
m2. It seems pOs were higher
29
by pineO and HYnek,
than f b
would bring
agreement.
Summaw
symmetrical
a radar
beam.
of 0,76,
0.76 ?I~.
has ar~ed
Bowles
is incorrect.
somewhat
daytime
lower
a value Te
and from
that,
For a parabola
We ha”e employed
a“ average
equation
to backscatter
the radar
that used by Bowles
observations
from
Even after
ent elevation, s employed
v:
with a tapered
feed,
V$ is indistin~ishable
equation together with the results
-29
m2 for tbe period
at a temperature
no systematic
repotied
reported.
Te = 1.6 Ti,
an attempt was made to correct
in the measure nlents,
by Pineo
and
Radar by a factor
of
= 0,33 and we have shown that this conclus-
for Millstone,
for electrons
made with a circu-
that employed
for the Millstone
value Um = 2.8 * 0.8 x ~0
than expected
= 2 Ti.
applicable
We have seen that Eq. ( 29) differs
Hynek by a factor
ion
da fiime
A value for Te:Ti
We ha”e deri”ed
larly
(41)
than would be expected
= 1.6, for which the average
sible that the discrepancy
.29 ,n2
unity.
in Sec. 11to obtain
This
average
but is compatible
the values
variation
from
is
with
of Nmax for the differ-
of Om during the daytime
was evident.
V.
CONCLUS1ON
From
Tables
re suits for the density
distribution
111and IV) and those of the spectrum
iation of the bandwidth of the signals
ing the density
ever,
distribution.
cause a distortion
above
The departure
in the electron
of tbe electrons
measurements
hmax is small
profiles
VI),
(summarized
conditions
obtained
in
we have seen that the var-
and hence cannot be a factor
fl.om equilibrium
density
above Nmax
(Table
near midday
influencwill,
how-
near this time.
54
%.-.—,
... . . ...-i---
It is clear
particles
temperature
in “iew
from the remarks
derived
from
Table
equilibrium
of the probable
a proper
correction
to see if they are consistent.
height measurements
(a)
be applied.
The scale
Eq. (3),
(Table
Iv)
values
We may,
Table
height of the neutral
both diffusi”e
ratio
however,
to the electron
and
lower,
but
on the sunspot CYCIe,
reinterpret
the scale
that have been made in the temper-
IX gives
the temperatures
when the fOllOwing assumptions
height Hi is related
!
equilibrium
will be somewhat
temperatu~e
by making the same set Of assumptions
ature zneasurements
the scale
The correct
of the electron-to-ion
cannot easily
for the scale
in Fig. 28 by assuming
(Te = Ti) are in error.
dependence
factor
height measurements
in sec. III that the values
IV and plotted
derived
from
are made:
and ion temperatures
by
k(Te + Ti)
Hi =
i.e.,
diffusive
,
equilibrium
is in operation.
(b)
The ratio Te:Ti appropriate
to the values for the scale height observed in
the period closest to midday is i.6: i for both summer and winter at all
heights above 300 km.
(c)
Oxygen
Assumptions
spectrum
is the principal
ion.
(b) and (c) are in essence
measurements
assumption
(Table
VI).
contained
Thus,
in the derivation
agreement
between
of the temperatures
Tables
from the
VI and IX would support
(a).
As shown in Fig. 44 where
tween the temperatures
this does not necessarily
sumption
mig
derived
these temperature
values
by the two methods
invalidate
assumption
(b) ] on the two measurements
for Ti are plotted,
is poor.
At first
because
the effect
(a),
is different.
the agreement
sight,
it would seem that
of the ratio Te:Ti
The ratio Te :Ti has little
effect
[as-
on the value
VALUES
OBTAINED
FROM THE SUMMER
DAY SCALE WEIGHT
\
//
.00
1
,//
t
j,/
P
/
400
/
d<
t
!
/
,00
VALUES OBTAINED
~:$M::;;TR”M
,L
I
-
400
KINETIC
55
—.
.
TEMPERATURE
[-K)
s
~
~
[
\,
VALUES
OBTAINED
FROM THE WINTER
DAY SCALE
HEIGHT~
Fig. M.
This figure provides a comparison of the
temperatures deduced directly
from the spectrol
measurements and those obtained from the scale
height measurement
after making certain assumptions I is~ed in the text.
be-
r’
for Ti deri”ed
~
from the spectrum
perat~tres
deduced
there will
be marked
seasonal
Fig. 44 to be superimposed,
would require
I
However,
tion,
i
that Te:Ti
tematic
errors,
variations
increase
in Ti,
density
profile
It seems
cannot be adjusted
sectio!l
by large
above h ~ax
the tem-
likely
the three
with hypothesis
cross
that unless the measurements
they imply that the region
this parameter
that they would have similar
with height [in agreement
to conclude
By varying
can be adjusted.
and we should not expect
would cause tbe scattering
so that the o“er-all
we are forced
in Fig. 36.
height measurements
though we might expect
such an increase
sequently,
measurements
from the scale
curves
slopes.
that
in
This
(b) in Sec. 111-D].
Vm to decrease
in propor-
amoutlts in this way.
Con-
are s~,b.iect tO seriOus sys-
Up to about 600 to 700 k,n is not in diffu-
sive equilibrium.
ACKNOWLEDGMENT
The author
wishes tO acknowledge
from Dr. G. H. Pettengill,
ant Gro”p
Leader.
who arranged
Thanks are also due to Dr.
for the computation
assisted in the construction
scribed
in Sec. III-B,
stone Radar staff,
dot.
M. LOewenthal
and subsequent operation
credit,
for the electrOn
a“d
Mrs,
received
V. C. Pineo,
Assist-
(then in Group 33),
W.A.
OF the spect.tim
Reid,
who
analyzer
de-
as d. many other members of the Mill-
too numerous tO menf ion here,
tO J. F, Mac Le.d
ond encouragement
and from Mr.
of the curves shown in Fig.34.
deserves special
OperOf iOn of equipmenf
is indebted
the cooperation
Leader of Group 314,
who were
concerned
density meOsuremenf$,
Mary Anders.”,
with
routine
Final IY, the OuthOr
who performed
most of the
reduction.
I
56
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