MILLSTONE HILL THOMSON SCATTER RESULTS FOR 1964
J. V. EVANS
Group 31
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ThCHNICAt REPORT 430
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MASSACHUSETTS
LEXINGTON
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ABSTRACT
1
Tlmmsrm seamer (incoherent backscatter)
at Millstone
fwo weeks.
of tbe ionosphere were made
1964, for 30-hour periods
density profile
and electron
and ion temperature. curves
The results are presented in this report, fogecher with the derived
variation
every
These data have been em?loyed to. derive tbe mean hourly F-region
to 700 km). electron
month.
observations
Hill at a wavelength of 68 cm during
(2.00
in each
seasonal:
of electron density (at 0600, 1200, 1800 and 2400 hours local time) and the
average daytime [0900 to. 1500). and nighttime (2100 to 0300) electron and ion temperature bebavicm.
Separate measurements
with a 23-cm radar permitted
ported to be. extended?o lower altitudes
the temperature
results re-
(-130 km) and, in addition, provided
infer-
mat ion concerning the ionic constituents behveen 130 amd 230 km . ..
Although 1964 -was at sunspot minimum,
evident.
variat”fon in foF2 was quite
It is shfilvn that rhis feature is strictly associated
and that dezsities
variations
U!e seasonal
of tempe+afure
phenomenon.
with the peak of the laye>.
above 400-km $Jtitude are highest W the equinoxe s.. No seasonal
are found which might .be large
At night the peak densities
enough to account .fcmthe
are highest in summer,
and the tempera-
tures at all .alritudes highest in winter.
This last effem
heat conducted from the proronosphere.
~which ix winter continues m he heated by
photoelectron
is believed
iargely due to
escape from the conjugate ionosphere which remains sunlit throughout
the night.
Accepted for the Air Force
Franklin C. Hudson
Chief, Lincoln Laboratory Office
~~
CONTENTS
Abstract
1.
Il.
1NTRODUCTION
68-CM
111. 68-CM
IV,
V.
VI.
C)BSERVING
DATA
3
REDUCTION
ACCURACY
DIURNAL
3
PROCEDURE
OF
68-CM
5
RESULTS
vARIATIONS
OBSZRVED
AT
68 CM
A.
Electron
Density
6
El.
Electron
Temperature
8
C.
Ion Temperature
SEASONAL
IONS
Zi
-
21
Temperature
24
VARIAT
A... Electron
Density:
B.
Electron
8
24
C :“ Ion Temperature
D:
VII
vIII.
1X.
X.
x1.
X111
Electron-@-Ion
PHOTOE
Temperature
LE.C TRONS
FROM
24
Ratio
CONJUGATE”
“1ONOSPHERE.
29
30
DISC USSION
23-CM
OBSERVING
23-CM
DATA
PROCEDURE.:
REDUCTION
32
Problem
ef Mixtures
B.
Electron
Temperature
C.
Ion Composition
35
D.
Checks
37
23-CM
of IorLs
30
.,,
32
A...
33
.Ze
on Results
3?
RESULTS
A.
Exospheric
B.
Electron
C.
XII.
6
Temperature
Tex
38
Temperature
40
Ion Composition
DISCUSSION
OF
37
23-CM
RESULTS
4i
4i
A.
Accuracy
B.
E-Region
Temperature
42
C.
E-Region
Thermal
Equilibrium
42
D.
Seasonal
Variation
in Composition
42
43
SUMMARY
A.
Daytime
B
Nighttime
C.
Daytime
D.
Nighttime
References
Electron
Electron
Electron
Electron
Densities
43
Densitie=
44
Temperatures
44
Temperature
45
46
MILLSTONE
HILL THOMSON SCATTER
RESULTS
FOR 1964
I
I.
INTRODUCTION
A Thomson
Wi?st ford,
scatter
(inkobesent
Massachusetts
backscatter)
(42.6-N;
7i.5”’W)in
radar
routine
ties,
electron
and ion temperatures.
Previous
these
data are
ga+he~ed
and the results”cd
sente.d in Ref. 2.. Here
mum in the sunspot
Based
plaintwo
increase
<eatures
and early
in f963”. Forthe
consider
ous ly. 2-4
However,
is. disc.ussed.
.Beginning
ing equipment)
to Place
ative
abundance
a number
of the heavy
with the 23-cm
radar
radar
Section
review
the method
and seasonal
reviews
the conjugate
The
ions as a function
and the accuracy
was detected.
VIII
1
tO ex-
ysteerable
antenna
than the grOund-clutter
supply
i.e.,
presents
simul-
and water
cool-
with the two systems
observations
temperatures
also yield
the rel-
the percentage
the results
by presenting
compo-
obtained
the 68-cm
In Sees. V and VI the diurnal
are presented
measurements
a full
and in Sees. 111and IV we briefly
of the F-region
Section
radar
obtained
of the results.
parameters
beating
study .?!hich
temperature
cannot be operated
power
we begin
procedure,
and
Previ-
at23-”c~~ wavelength
of ion and electron
report
observed
gOod,
given
of F-region
greater
of altitude.
This
descriptions
systems
radar
that follow,
.
-——..
curves
23-cm
the observing
the 23-cm
at a range
the results
to construct
as those
is remarkably
employs
the transmitter
and NO+ ions.
of the observed
ionosphere
(e. g.,
by comparing
in which predawn
X11 present
echOes
therefore,
cQnjug?.!e ionosphere.
OPerating
radar
tO ex-
and equ’inox
by recent.theoretical
The two radar
In the sections
11presents
the. same
of results
tO mOrphol Ogical
the 23-cm
obliquely.
and light
of reduction
variations
observations
tions 1X through
pre-..
to be at: the mini-
.we have attempted
va~iztionsthatare
which” p”oint to the existence
130 to 800 km.
in 1964.
in *963,
the two sets
have been questioned
Because
However,
from
diucnal
a secOnd radar system
it has been possible
interval
Obser~ed
resultsand
of components
of 0+ ions and the qum of O;
results.
i.963 were
a“t Millstone
Hill;
the summer
3,4
It isof interest,
winter increase.
the iOnOspheric
the beam
are shared.
the height
for the year
‘1964, ..which happened
of fast pbOtOelectTOns.~p.@.~the
200-km. altitude.
times,
over
from
to. the
presented
with the arrival
because
observations
of foF2
between
$hese explanations
by directir+g
at different
yield
agreement
ableconfidenc.e.
it is possible
taneously
sition
the 1964 results
below
interference
temperature
(predawn)
in 4964, we employed
regions
system,
morning
New resultsare
associated
Hill,
measurements
.of F-region
electron
densi1,2
have outlined theproceduresb
ywhich
for. the year
in the behwior
most part,
this lends
plore
results
upon the diurna.l vaPiatien..0f
to. see to what extent
rises
we present
at Millstone
cycle.
anomalous
evening
and reduced,
reports
has been employed
and discussed.
Section
due to photoelectrons
discusses
tbe 68-cm
in this same
order,
VII
arriving
results.
namely,
Sec-
...
TABLE
INCOHERENT
BACKSCATTER
I
OBSERVATIONS
Begin
End
(EST)
(EST)
G
- 19t
Mean
K
P
—
4 January
1530
40
10 January
0900
11 January
1600
2+
18 January
1600
1600
20
3+
1530
20
1500
2+
1600
20
1600
o+
3 January
17 January
1000
31 January
1030
1 February
14 February
1030
15 February
28 February
1500
29 February
13 March
0930
14 March
27 March
0900
28 March
c1
Q
10 APril
0900
11 April
1600
2-
24 April
0930
25 April
1600
2–
8 May
0930
9 May
1700
0+
22 May
1130
23 May
1500
1-
Q
14 June
0800
15 June
1500
2–
27 June
0030
27 June
1500
10
10 July
0800
11 Jdy
1500
2-
24 July
1000
25 July
1530
1+
1600
2–
1530
2-
I 430
1530
20
10
7 August
0830
8 August
21 August
1100
22 August
4 September
0800
5 September
18 September
0800
19 September
q
Q
2 October
0800
3 Octcber
1500
1+
16 Cktober
0800
17 October
1500
1+
30 Octcber
1100
30 Oct05er
Q
1630
1-
6 November
0900
7 November
1-
13 November
14 November
Q
Q
1600
0900
1500
0+
27 November
0900
27 November
q
1500
0+
3 December
0900
1600
10
0900
4 December
18 December
q
17 December
0900
30 December
I 530
1600
20
10
29 December
—
—
observations,
reduction,
accomplished
with both radar
II.
results
OBSERVING
68 -Ckf
usually
the interval
profiles
time
over
January,
Several
the profiles
I lists
operation,
but these
68-CM
made
tended
by gating
the frequency
broadening
spectra
the time
in order
reduction
the sensitivity
for later
gathered,
of
of
non-
and indi-
It can be seen that apart
magnetically
to increase
to ob-
in the amount
of the signals
were
required
1964
Thus the number
these periods.
was operated
from
Perkins
Ti.
quiet.
its reliability
and ease
of
of the apparatus.i
gating
obtained
The error
spectral
(Ref. i)
equal
in length
by transmitting
the receiver
byusing
a pulse
private
weight
the radar
signal
of $0 percent)
function
tbe
in the
pulse.
That is,
hut the additional
an entirelyney
set of theoretical
which allows
communication).
at
from
introduced
to the transmitted
for,
spectra
arose
of the distortion
was allowed
Thus,
was not.
the proper
and T. Hag fors,
from
(of tbe order
shapes
base a portion
introduced
have been computed
(F.
alter
This
some
During
but the time
to one hour.
could
Observa-
intervals.
which tbe data were
index Kp during
and ion temperatures
of expected
from
smearing
arising
tal effects
during
measurements
approximately.
to two weeks,
by recording
to the equipment
to overestimate
in the computation
receiver
of the work
REDUCTION
to ~964 the electron
Hill
a summary
at weekly
than in 4963.
the periods
did not appreciably
DATA
Prior
Millstone
less
the days on which the equipment
were
90 minutes,
at a time
was reduced
was accomplished
Table
changes
and temperature
was increased
only about 25 percent
processing.
density
once every
profiles
the mean value .of the geomagnetic
neglect
which
of 30 hours
periods
and temperature
were
to produce
from
III.
range
for periods
observing
density
obtained
real-time
cates
height
conducted
between
tain complete
X111 provides
systems.
(about 200 to 800 km) was examined
tions were
Section
PROCEDURE
In i 963 the complete
be made
and discussion.
for
The power
these instrum en.th filter is
I
intbe
,,
Pi(f)ob~
=~+-m
<, S(f)\ ’>avg
(1)
:i(f)df
.,,
where
.th
is the power spectrum
at the output of the receiver,
Fi(f) is the power of 1
\
and f is frequency
shift measured with respect to the translated
radar frequency.
<l S(f)[2)avg
analyzer
filter
Thepotier
spectrum
<1S(f)l
<l S(f)12>avg
-- f+-
‘>avg
presented
to the spectrum
d“<,H(”to,,’>avg ~
,2T(:
“)12
analyzer
[~
filter
bank is
‘;:;!! ;,:)’l
-
(2)
-m
where
<l H(uto)12>avg
(as a function
Tbe equations
Besides
is tfie spectral
of frequency
for
being
a function
that this latter
approximate
of Te/Ti
v) corresponding
of electron-to-
the spectral
dependence
electron
and Ti were
density
(of a CW signal)
to a delay
have been given
<l H(uto)12>a”g
and ion composition,
lier
broadening
ion temperature
shape depends
could be handled
profile
from
then established
to and ,
by a number
introduced
by the ionosphere
is the pulse
of authors,
ratio
Te/Ti,
length
e.g.,
ion temperature
upon the electron
density
by obtaining
the experimental
which the density
by comparison
from
N.’
signal
spectra
3
—-
..-.-..
.... ..—.$—.
Ti
It was shown ear-
N could be estimated.
of the observed
employed.
Fejer.5
mti,?-.
results
an
The values
with one
computed
ties
for the same
were
5. Oandi
worked
OMHz
out,
(N=
Mills tox.. Hill
density.
namely,
will
cOrrespOnding
tO Plasma
~
Following
the suggestion
be correct
the true ratio
if fN >5 MHz.
spectral
for
fN = i.o,
different
+.5,
20,
FOP wavelength
shape ceases
densi2.52
in use at
to change
when
have been computed
OnlY fOr the case ‘N =
these
to derive
of Moorcroft,6
and the derived
(Te/Ti)
sPectra
of cases
fN in MHZ).
that the signal
theoretical
number
frequencies
in ~lectrons/cm3,
(k = 68 cm) it transpires
and Ti which will be correct
Ti
only a limited
i.24Xi04f;,
fli ~ 5 MHZ”
In the new computations,
io MHz.
In practice,
are employed
If the plasma
electron-to-ion
frequencY
temperature
is less
ratio
values
than ‘5
(Te/Ti)’
of Te/Ti
MHz,
OnlY
will be related
to
in
(3)
.,,
I
!
where
a = k/4nD and D =
when the density
ter to produce
J---T
(kTe/4vNe
N is expressed
a set of curves
The procedure
for
in electrons
analyzing
two quantities:
f the width in kilohertz
ity,
and x the ratio
of the peak intensity
yieId
are inserted
values
lined previously
equality
on a graph
of Ti and T;/Ty
except
(Te > Ti)
It follows
off,
appropriate
employed
length
profile
spectra
and a value
employed
for
mat-
are scaled
to
of half-peak
intens-
frequency.
These
(, . 0.5 or f. Omsec)
is then obtained
to correct
simple
N and T~.
to that at the center
to the pulse
density
c! . 0.785-
that it is a relatively
given
the center
(in the wings)
The electron
that the factor
6,7
between
Millstone,
The signal
the data is now as follows.
yield
values
/cm3.
which Te can be read
from
For
) IS the 13ebye length.
the effect
in the manner
to
out-
of the temperature
in-
becomes
N(true)=
~ +~:fT,
(4J
N(obs)
1
which
is a closer
approximation
N(true)=
than used hitherto,
~ +~e/T,
f,2
namely
(5)
N(obs)
1
,,
Given
the true density
N at the height
where
the temperature
value
of Te is obtained
by interpolation
from
a plot of Te w
As in the past,
the radar
is established
From
for
the method
data only for
by normalizing
all these
each month.
data,
is then assigned
and ion temperatures
is drawn
through
stant density
the day.
of data ooints
of hmaxand
These
as a plasma
This
*Z5,
of N ~axf?2
vertical
frequency
type of presentation
For
Nmax.
profiles
fN)
*iOO.
. km,
a mean profile
are constructed
density
measured
N/Nmax
with respect
and temperature
the greatest
shape.
profiles
the mean
and the best smooth
are then used to plot contours
provides
upon
with an ionosonde.
with the correct
the temperature
are computed,
above.
at all heights
profiles
that the relative
+75,
the true
depends
density
observed
and temperature
*50,
sampled
are constructed
The absolute
this requires
which yields
at the heights
points.
N (expressed
over
the number
these
e.g.,
is obtained
the mean value
electron
and time
intervals,
N,
density
was made,
T~ and N [Eq. (3)] as outlined
profiles
to the value
electron
of the density
at fixed
density
of the profile.
the peak density
A mean of these
to the peak,
and shape
mean hourly
In the case
must be determined
This
by which the electron
the height
measurement
curve
of con-
as a functiOn Of height
amount of reduction
in
obtained.
4
———
-...,,.,
_-.__._,,,
,._
A
In addition
for
to the analysis
each month are
constructed
to 1500 EST and from
plots
1
of isothermal
ployed
IV.
to infer
daytime
OF
are
were
There
i.e.,
center
are
with tbe pulse
included
temperature
measurements
or less,
percent
tudeby
At the highest
The
evidence
borne
exact
ployed
225-km
altitude
chiefly
(*35km
during
the first
of systematic
altitude
percentage
error
The error
of this effect
the value
observed,
of NO+ or O:
approximately).
as a consequence
in lowering
(>600km)
at temperate
ions
in the
appears
of Ti obtained
measurements
of the transition
soundings
the behavior
obtained
to be
at this alti-
neath the satellite
with the Ahmette
itudes 48” to 60”.
Using
mation
the i~n composition
emission
i 000 km above
together
MiIlstone
centered
ionosphere
from
m which
taken as close
(L . 3.5),
case
ion.9
to the total
the foregeing
one scale
beigbt
(i. e.,
-200
that the light
tude that can be examined.
ence of light
I
could
km) below
less
with certain
tbe satellite
(i. e.,
lies
has emassumptions
to infer
the transialtitude
(de-
> i 000 km) dur-
sufficiently
find less
be determined
at the satellite.
be-
frequency
At a height
than 20% H+ ions during
rocket
indicated
that this is typical
<t &.,
the cutoff
flights
behavior
concerning
of
6-hour
into the top-
that He+ never
at sunspot
the H+ abundance
bemini-
may be
ions.
at which temperature
determinations
800 km by day and 600 km by night) lies
is of the order
altitude
that the error
than postulated
at all times.
of iO percent
or less
introduced
at the highest
by the neglect
earlier.~
I
,.
at least
We may expect,
5
—.
indirect
Watti’
that the transition
The only recent
the transition
Thus we believe
no satellite-
yet by various
by determining
that the upper limit
(approximately
ion abundance
ions is substantially
et al.,
.—
mean time.
of light
of
certainty
only over the range of dip lati2
~ $.,
were able to infer some infor-
altitude
of Barrington,
abundance
ions
the day than at night
this period.
of the transition
of the F-region
has suggested
it would appear
can be made with this apparatus
therefore,
height
of light
overestimate
Unfortunately,
together
above
Barrington,
at 1000-km
ion composition
Bauer
lies
The altitude
Barrington,
the estimates
during
with altitude,
Watti i finds
with reasonable
with the scale
which
1 sounder,
(73”),
satellite,
on 0600 and 1800 local
the predominant
From
ttie Sime
for
and ion temperatures
tbe night.
that it can be located
concerning
has been inferred
of Millstone
number
smaller
0+ ions to He+ and H+ ions is known to be low-
50% He+ or H+ ions)
of 50% 0+,
that a small
of Ti and a somewhat
for i 964 have been published,
altitude
of the electron
At the dip latitude
as tbe height
periods
is the possibility
that it is higher
10
than over the equator.
latitudes
ing the day and at >900 km during
of a V LF
there
of the transition
region from
8,9
There
is
also
evidence
minimum.
topside
tion height.
came
may be em-
of th@se is that only 0+ ions are presthat at the lowest
of the pulse
height
the height
concerning
mum?
plots
sources
with an appreciable
would lead to an overestimate
mass-spectrometer
methods
,.
(See.XII-A)
regions
and is significant
and that it is higher
side
0900
then used to obtain
These
bothersome
the principal
The first
the analysis.
extent
for
which were
error,l
Accordingly,
at 225 km,
altitudes
This
est at sunspot
fined
are
year.
from
about 50”K.
are present.
T~.
during
vertical
–io
curves
the entire
the periods
profiles
variations.
of instrumental
is some
by the large
during
temperature
RESULTS
made
ent at all heights.
These
respectively.
seasonal
eIiminatedbyi964.2
the assumptions
and nighttime
all the data obtained
and month for
and nighttime
68-CM
mean daytime
by averaging
vs height
It is thought that sources
half of 1963,
above,
Zi 00 to 0300 EST,
contours
ACCURACY
outlined
.,,
,,.
alti-
of the pres-
V.
DIURNAL
Figures
VARIATIONS
i through
each figure
(a) contains
OBSERVED
12 present
AT
68 CM
the results
the results
for the months
for the electron
January
density,
through
(b) the electron
December.
In
temperature
and
(c) the ion temperature.
A.
Electron
Density
The behavior
similarity
midnight
two hours
from
of the electron
month
and falling
after
being fastest
after
to month.
between
ground
density
For
midnight
sunrise
[Figs.
l(a)
example,
12(a)]
hmax is always
and dawn.
(Table
through
The value
111and thereafter
shows
a striking
highest
(-290
of hmax reaches
tends
to rise,
degree
of
to 300 km) near
a minimum
with the rate
about
of increase
sunset.
TABLE
SUNRISE
(X = 98.5°
AND
AND
SUNSET
cd Ground
II
AT
Level)
ITS MAGNETICALLY
Mills!
(42.6”P
100-KM
FOR
ALTITUDE
MILLSTONE
CONJUGATE
HILL
POINT
~ Hill
Coniugote
1.5”W)
(7 I . 9“S 80. 7“W)
Point
Sunrise
Sunset
(EsT)
(EST)
1 January
0629
1709
15 January
0628
1722
1 February
C617
1742
15 February
0602
1759
1 March
0541
1816
0220
2251
15 March
0518
1832
0405
2059
Date
=
tlt
Always
sunlit
I
\
1 April
0448
1853
0531
1523
15 April
0423
1910
0632
1814
1 May
0356
1930
0737
1703
15 May
0337
1948
0831
1607
1 June
0320
2007
0928
1512
15 June
0315
2017
0958
1447
1 July
0320
I 454
0330,
2019
2012
0958
15 Juty
0528
1528
1 August
15 August
0350
1955
0832
1627
0407
I 935
0735
1720
1 Sepfember
0428
1905
0619
1S29
15 September
0444
1839
0508
1929
0501
1811
0334
2051
0516
1747
0134
2244
1 November
0526
1713
15 November
0552
1709
1 Octcber
15 Oct&er
I December
0519
1700
15 December
062 I
1700
t
t
Alwoy~
sunlit
-!_L_!_
6
,,
The electron
density
maximum
zround
it is ciear
that at fixed
increases
throughout
noon or shortly
heights
thereafter,
until the ever. ing increase
of a separate
3.which suggested
rise
article
to a collapse
summer
this is sufficiently
Variability
in the increase
has risen
during
proposed
as the prime
ward
were
well
peak is already
This
of electron
to reach
value
during
at this time
in electron
though the rapid fall
influence.
that are responsible
The evening
in foF2
(a) in winter
for
only during
the fall. in .T:
equinox
was
the layer
up-
in all months
and summer.
large
is less,
of day.
temperature
is evident
is neither
above. h.max that can participate
In
to which hmax
driving
increase
sunset
at the peak.
Thus,
the forces
{n the after-
temperature
in the density
its highest
a
is rising,
has been the subject
to the height
agent,
of ionization
It
nor rapid,.:(b)
and (c) the density
in
at the
high.
explanation
has been challenged
the time-dependent
continuity
are allowed
to vary
dec.reaseat
sunset
not able to give
tbe prime
tends to decrease
day to day cotild be related
a modifying
that this is because
tbe amount
for foFZ
from
and tends to reach
the fact that the layer
phenomenon
and an increase
hmax hut can be recognized
above
was suggested3
that the rapid fall
of the day
physical
This
occurs.
thickness
pronwdnced
of foF2
the course
thought to exert
at heights
winter
in the layer
at all altitudes
for
to hmax the density
with respect
noon at all altitudes
gives
the morning
If one allows
cause
and Venables:
eql.mtion for the F-region
independently.
is capable
rise
by..Thomas
Their
of causing
to increases.
results
show that,
tmdiffuse
is tbe temperature.
density
dependence
who. succeeded
when the electron
ionization
in electron
i3
in solving.
and ion temperatures
though tbe electron
temperature
to lower
this in itself
altitudes,
as large. as observed.
of tbe principal
loss
They
mechanism
is
sugge,st: that ~
at F-region
heights, namely
~+;Nz.+
NO++
e-.
If the N2 molecules
efficient
tional
crease
(6)
N+
(7)
O+hu
which take part
would be a function
temperature
N~:+N
has a similar
variation
In summer
the evening
maximum
effect
rise
maximum
only above
change
in foE’2 is larger
tends to be larger.
In winter,
about 300-km
excited,
Thus,
the effective
if it is assumed
to the electron
to a marked
13
of ion~z ation near the peak.
an accumulation
an observable
temperature.
diurnal
in Te at sunset wotiidgive
the midday
[Eq. (6)] are vibrationally
of vibrational
temperature,
in tbe loss
rate
tbe rapid
altitude,
noted,
so that foF2
in
but in equinox
the evening
shows
co-
de-
and could result
than the noon maximum,
as already
rate
that the vibra-
increase
a single
is
midday
maximum.
In summer
and equinox
ter this decrease
near
0400.
suggested
whole
is arrested
Above
that this redistribution
protcmosphere.4
A closer
it is less
near
examination
at all altitudes
in the F-region
that such cooling
tbe night.
which could cause
below
throughout
throughout
is caused
would be most
a significant
there
change
is no change
in the pitch
It has been
by the cooling
serious
of the sun at the conjugate
Further,
In win-
occurs
the night.
of sunset when the sun’s
disiance
the night.
450 km and a maximum
to be decreasing
or in tbe absence
of the zenith
than ~ . 90- throughout
the sun and tbe field
appears
of ionization
It was supposed
hemisphere,
decrease
22oO EST at heights
500 krh the density
set in the conjugate
large.
tbe densities
following
point shows
--,.-..,
,
distribution
r
that
@ between
7
..—–...—.
sunbecomes
zeriith angle
in the angle
angle
of the
.
,;
and
hence
the escape
suppose
sible
that the reduced
for
reduced
temperature
jugate
i4
rate of photoelectrons.
loss
decline
electron
rates
The most
temperahre
explanation
that accompanies
and consequently
must be sought
plausible
the density
in the behavior
at this time
the density
increaze
itself.
is to
increase
is respon-
The reason
of the @otoelectron
escape
for a
flux at the con-
point.
Electrcn
B.
During
Temperature
eq,uinoctial
months
ture [Figs.
3(b),
throughout
the day and falls
temperature
observed
4(b),
gradient
mum at some
months
altitudes.
[Figs.
In winter
sunlit,
it *8 probsble
photoelectrons
Iota.1 ionosphere
During
tude.:
rapidly
[Figs.
i (b);
(-3 ‘/km),
that. during
behavior
morning
temperature
is
maxi-
i 2(B)] the temperature
but the actual
the electrcn..temper2ture
is a POsitive
temperature
to be an early
1+ (b),
tempera-
at all altitudes
the day there
electrcm
appears
2(b),
constant
During
Similar
though there
the electron
is roughly
at sunset.
at all altitudes.
months
and October)
at sunrise,
gradi-
near
lImaxF2
the w inter
muntbs
the proton osphere
exceeds
when the cOnj.ugate hemisphere
and contriiiute
to the nocturnal
remains
heatitig
of the
[Sec. VII).
the short
summer
to warming
night the electron
the temperature
9(b)j and then incneases
occurs
reaches.
hi winter
again.
only2
temperatu~s
is roughly
a minimum
the same
hou~s a~ter local
a little
before
thing happens,
sunset.
constant
except
at a given
alti-
midnight {Figs.
41b), “.
that the reversal
This behavior
is belibve.d
from
to be a
cons equence of the fact that the proton mpher ic heat flux is roughly constant throughout the
i6
and the heat loss (from electrons
to ions) initially exceeds
the input, but later as the den-
night
sity
decreases
this situation
C.
Ion Temperature
The
diurnal
pei-ature,
variatiOn
thereby
demonstrating
remains
night.
Ti shows
In winter
EST when the electron
and causes
given
gesting
electron
neutrals,
above,
little
cause
temperature.
Below
but the values
appears
and effect
[e. g.,
between
is greater
lower
During
the daytime
the
Ti declines
throughout
the
appreciably
rapidly.
Figs.
heating
‘em-
i(a),
till
’200
In Ref. 4 we argued
2(a)] which occurs
and cOOling.
at this
In the tentative
have been reversed.
gradient
above
i(c)
— i2(c)
the night in equinox
than during
400 km is of the order
than that of the neutrals,
300 km the ions are probably
During
the two.
In summer
and does nOt decrease
in density
in the balance
shown in Figs.
somewhat
between
is also found to be declining
temperature
that the ion temperature
tends tO fOllOw that of the electron
coupling
of sunset
of the increase
reversal
altitude
at all altitudes.
evidence
the daytime
ably too low (See. IV).
dTi/dh
constant
temperature
a second
In all seasons
the thermal
fairly
that this was a consequence
explanation
is reversed.
of Ti abO~e 300-km
ion temperature
time
1
the ion temperature.
This
~.
i5
as argued p.r.evious Iy;
by the PCO!.OnOsPhere
Of heat supplied
traverse
In the equinoxes
cooling
less
than LJ .su.mmer
is thought to be” “a consequence
September
rapidly
6( b]-8(b)]
At night in all fieasons
however,
April,
rises
somewhat
300km. is higher
is lower.
(March,
i o(b)]
of about 2-/km
in summer
ent above
9(b),
(toward
8
and is converging
in good thermal
the bottoms
and in summer,
the day (-’1.5 ‘/km).
of 4 “/km,
equilibrium
of the figures)
the temperature
sug-
on the
with the
are prob-
gradient
I
-@@IL
,00
,00
so.
:
(0) Plasm.
frequency.
Z
5
❑
z
400
300
m.
EST
TEiE@
,00
700
,00
,00
,00
,00
z*
:
k
g
:
!
w
❑
I
400
.00
,00
300
,00
,00
048!2
0.812!6
16202,
m>
EST
EST
(b) Electron
temperature.
Fig.
1.
(c) Ion temperature.
Mean
monthly
behavic.r
for January
1964.
I
9
.!
EmizL
~EoRuARy
,9,64
,00
PLASMAFREQLENCY[MHZ]
600
600
~
(0) Plasma frequency.
=
g
.00
ZOO
0481216
?0,,
EST
30.
K
t600
1400
!20(
200 ~
.
(b) Electron
EST
EST
(c) Ion temperature.
temperature.
Fig. 2.
Mean
monthly
behavior
io
for February
1964.
7,0
-J
0.5
R
1,5
,00
MARCH
t.5
2,0
1964
PL4$MA
FREQUENCY
[MHz)
2.5
,00
:
:
1.0
(0) Plasma frequency
3,0
:
.
z
.
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4.0
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EST
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2000
K o
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4000
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20 0
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EST
EST
(b) Electron
temperature,
Fig.
3.
(c) Ion temperature.
Mean
monthly
behavior
For March
1964.
(.)
Wm.
freq.e.cy.
(c) b. temperature.
(b) Electron
temperature.
Fig, 4.
Mean
monthly
behavior
for April
1964.
1.2
—
,..
(a) Plasm frequency.
EST
1
200
1
1
1
!
1
1
04812
EST
EST
(b) Electrcm
(c) !0.
temperature.
Fig. 5.
Mean
monthly
behavior
for May
1964.
temperature.
1
I
$6?02,
1
1
(a) Plasma frequency.
EST
EmmL
7’30
,0,
500
j
>
g
‘#
400
300
,00
b
300
800
,,
1
!
I
1
1
1
04a
0
(b) Electron
1
200
E’:T
EsT
(c)
temperature.
Fig. 7.
Mean
monthly
behavior
for July
1964,
Ion temperature.
1
,,
1
1
m
1
I
24
(a)
PI mm.
frequency.
ES1
EST
EST
(b) Electron
(c) !0.
temperature.
Fig. 8.
Mean
monthly
behavior
for August
1964.
temperature
(a) Plasma frequency
EST
EST
(b) Electron
(.)
temperature
Fig. 9.
Mean
monthly
behavior
’17
for September
10. temperature.
1964.
(.)
P1.smo frequency.
EST
EST
EST
(b)
Electron
(.)
temperature.
Fig.
10.
Mean
monthly
behavior
for October
Ion
1?64.
temperature.
(.)
pl.smo
frequency
Em@
@zimL
700
700
600
,00
,00
500
-j
g
!
:
:
:
g
Y
400
400
300
300
200
0,8
!6
m
m,
,.
O,*I2
16202+
E’:T
(b) Electron
EST
temperature.
Fig.
11.
(c)
Mean
monthly
b.havior
19
for November
Iontemperat.
1964.
re.
(0)
Plasmo
frequency.
.mmL
E$T
(b)
Electron
(c)
temperature.
Fig.
12.
Mean
monthly
behavior
20
for December
Ion
1964.
temperature.
vI.
SEASONAL
A.
VARIATIONS
Electron
Figures
13(a-d)
1800 hours,
showing
Density
respectively.
seasonal
density
Above
cause
the number
values
increase
that occurs
from
peak densities
lower’
electron
In all seasons
see Sec. VIII),
Table
If gives
the time
and later
in error,
tend
is
a
of foF2
at these
of foF2
immediately
N ~ax
above
to a value
in Table
being
to
and the mid-
What is rather
surpris
from
variation.
electron
This
-
tbe
density
arises
scale
at about ionospheric
be-
heights
density
begins
sunrise
tO increase,
(X
-
100”,
~Vhich OCCUrS
witier
as a result
is faster
above
is rising
of the plots
illustrates
clearly
of about
rotation
densities
above
That
time.
interval
tbe mean and the error
seasonal
highest
anom-
is strictly
densities
measurements.
near
hmax.
The figure
ma;, be
which this graph
that the anomaly
than at any other
Tbe two profiles
times
these
from
400 km or above,
by Faraday
the height
at 0600
Fig. t 3(c) that the tOtal cOntein~ ~2~Oo N
from
substantially
rapidly
the so-called
It is striking
before
shown in Fig. i 3(b)
extremely
shown in f?ig. 13(b) for
of greater
in winter
tbe peak.
required
shows
bars
the
the peak of the layer
is,
tbe density
This
decrease
is shown most
for the density
the mean monthly
nearest
Thus,
Ch
to fall
variation
from
of this
noon on each of tbe days listed
are probable
errors
is only an annual variation
derived
from
in this parameter,
of the lower part of the layer also varies smoothly from a sum18
This striking change in layer shape has also been demon-
minimum.
variation
in the “ slab thickness”
parameter
i7
Thomas19 has discussed
measurements.
perature
presented
Ti or Te/Ti.
13(c)]
variation
an artifact
than in summer,
This is confirmed
arise
semithickness
a
from
as a consequence
The seasonal
in winter.
rotation
results
and it can be seen that this occurs
It can be seen that there
that might ,result
in Te,
sunrise
At an altitude
at noon in 1964.
by the seasonal
Faraday
by lower
the electron
and it is evident
used to compute
maximum
from
months,
In large
In part this results
seasonal
to rise
in winter.
[Fig.
tie have plotted
of the values.
The parabolic
strated
begins
the contours
in the profiles
0.7 Nmax
1 were
the minimum
mer
months,
times.
the layer
parameter
the scatter
plots
(Sec. v-AI.
show Iiltle
13ecause the density
in winter
in winter
in h“ig. 14 where
thickness
than they are.
are offset
befOre
of this effect.
which are not reflected
clearly
in winter
of ionospheric
in the equinoxes,
maximum
in summer
sunset.
than this time
of the peak of the layer.
high values
latest
since
(in summer)
The noon behavior
values
to occur
occurs
lower
or the other
than in winter.
elapsed
and the May peak is perhaps
was constructed.
a feature
in summer
increase
temperature
in the equinoct ial and summer
aly, of higher
diagrams
noon and
– 12(a- c).
of hours
densities
40 to 50 minutes
a.onsequence
somewhat
to these
‘l (a-c)
0600,
sunrise.
0600 in summer
is chiefly
at midnight,
(and ion) temperatures.
tbe electron
i. e.,
at about ground
density
applied
to Figs.
are higher
are not actually
about 400 km the midnight
the higher
arising
hasbeen
the sunset
reflect
in electron
in contrast
the peak densities
because
values
ing is that the winter
nocturnal
(below)
[ Fig, 13(a)]
this arises
night density
variation
No smoothing
variations
At midnight
measure
show the seasonal
changes
in Te,
in the following
Thus the seasonal
of large
Ti or ‘re/Ti,
changes
the changes
and found that these
sections
variation
[= (./’N db)/Nmax]
show that there
in Te and Ti as suggested
21
in layer
are small.
is little
of the slab thickness
determined
seasonal
apparently
by Yeh and Flaherty.
shape
Tbe
tem-
variation
does not arise
17
700
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The sunset
servable
phenomenon
equinoctial
begins
fore
increase
The electron
to decrease
some
ionospheric
sunset
increase
simply
(Table
B.
Because
reaches
sunset.
a
Thus the
of the fact that the sunset
later
Electron
and the elec-
II)
which follows
is occurring
it occurs
be-
shown in Fig. i 3(d) arise
as a result
increase
mer
maxima
and
temperature
30 or so minutes
peak at about ionospheric
equinoctial
is an ob-
only in summer
months.
tron density
in density
near +800hours,
and in winter
In sum-
not at all.
Temperature
the variation
of electron
and ion
,964
temperature
Fig.
14.
Seasonal
parameter
variation
of the thickness
h7@A - hmax.
with time
tends to be small
noon and midnight
[Figs.
have taken 6-hour
averages
near
I(b, c) to lZ(b, c)],
centered
we
on these
times.
Figures
(2io0
‘t5(a-b)
show the variation
to 0300) electron
sonal variation
temperatures.
below
300-km
a summer
minimum
is a very
pronounced
seasonal
sequence
mains
uniformly
of a higher
sunlit
C.
Also,
made
shown in Figs.
temperatures
results
[Fig.
300 km there
maxima,
i5(a)]
appear
and mean nig~ttime
show no pronounced
to be real
variations,
as noted in ‘t 963 (Ref. 2).
The temperatures
are lowest
As noted in Sec. V,
in summer
arriving
but not in summer
seafor
At night there
?June
and July)
this is thought in part to be a con-
beat flux due to the fact that the conjugate
fast photoelectrons
in winter
for
above
i6(a-b).
are clearly
electron
in winter
in Ti at night is considerably
of nocturnal
perature
is so low in August
this month
D.
(Table
heating.
from
the conjugate
ionosphere
r:-
ionosphere
serve
(Sec. VII).
Figures
foregoing,
i7(a-b)
values
i7(a)]
values
[Fig.
are encountered
spectrum
lies
i6(b)].
Temperature
is somewhat
peak always
[Fig.
higher
profiles
between
than for Te,
indicating
different
activity
to the ion tem-
trend,
but at night the
The summer-to-winter
that the latter
can be offered
from
be applied
show no seasonal
in summer.
The magnetic
dif-
is a far better
for why the nighttime
tem-
on the days of observation
that encountered
in any other
in
month.
Ratio
show the variations
the daytime
the lowest
less
averages
can partly
and lowest
No good explanation
1) was not particularly
Electron-to-Ion
temperature
The daytime
highest
indicator
computed
trend.
(0900 to i500)
Ion Temperature
perature
[Fig.
and equinoctial
protonospheric
ionosphere
The comments
ference
Above
into the winter.
in winter.
to heat the local
The daytime
altitude.
example,
and increase
of the mean daytime
of Te/Ti
over
the year.
i7 (b)] show no pronounced
in summer
and the highest
than the peak value
employed
reported
for
comparison
300 and 350 km,
irrespective
As may be expected
seasonal
in winter.
previously.2
in 1963 were
of season,
variation,
from
while
at night
The peak daytime
This
inaccurate
is because
the
value
the
[Sec. 111). The
and has a value
in the range
24
..—.
,-
..—-...,,,..“..
,.— —. ........-_..
__,__,
.—
ELEcTRON
5!$2551S
JAN
!S51$25$1$?551$
FEB
MAR
&PR
Average
(.)
DAYTIME-1964
TEMPERATURE
,,,1, (,, ,1, ,, (,1(,,,,
,00
255152
MAY
FEB
MAR
(b)
Fig,
15.
APR
Average
Seasonal
5! S? S5,S?5
JUI.
(0900
AUG
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nighttime
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OCT
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JUL
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variation
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TEMPERATURE
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,AN
$5151>
JUN
daytime
ELECTRON
’00
1,~
AUG
to
0300
of electron
SEP
25,1
OCT
hours).
temperature.
$2s51$?5
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DAYTIME
ION TEMPERATURE
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A,.
Average
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nighttime
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variation
26
to
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0300
hours).
of ion temperature
(52,$1323
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DAYTIME-1964
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daytime
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FEB
MAR
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(b) Average
Fig.
17.
$13 2S5,S,$,
MAY
JUN
nighttime
Seawnol
$5,,
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(2100
voriation
27
‘.
-1964
,,,
?,5,,
,$ ,,$,,
AUG
sw
OCT
to
0300
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of Te/T.,
\;>
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,,,
NW
,5,s
DEC
mm
13.3! -10358111[
/
ELECTRON
,800 –
300
TEMPERATURE
/
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~11
APR ,964
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,.00 /
:
,.
(400 –
,,00 -
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am
1
,
,
#
,
1
,22300,
.2
03040506
[
EST
Fig.
Solid
18.
Variation
~rrows
of
indicate
ken arrows indicate
Te
showing
predawn
time of cmset of Ioc.I
time at which
conjugate
increases
heating
point
Fig.
coincident
with
as estimated
heating
19.
conjugate
from ATe/dt
sunrise.
and brO-
~
commences.
Times
sunrise heating
Time at which
at which
appears
local
and
to commence
sun’s zenith
distance
coniugate
(Fig.
18).
is 106” and
98.5”
is also indicated,
These two angles corresP”d
to e~rth’s shadow,
reaching
200 and
100krn,
o
,,,,
1
15 FE@
I
I ‘AR
L
15 ‘“
II
t .,.
DATE
28
respectively.
from
2.6 to 3.o.
At 6oo-km
to lie at about the same
to 2.7 in winter
about i.4
vff.
in summer
to about i.6
In Ref. 2 we drew
early
Since
morning
source
zenith
from
to occur
throughout
effects
zenith
are first
point.
possible
Because
36 minutes
of time
at the conjugate
does provide
the
served
Fig. 18 the times
for
behavior
(L -
3.2) it is possible
to rise
is similar
sunrise
the temperature
appears
to rise,
group
at Nancay
i 964).
This
(L - 1.8),
to almost
its full daytime
The difference
in the behavior
value,
are
to establish
associated
that noctm-nal
with conjugate
The time
local
sunrise,
reach
following
sunrise
causes
greater
transparent
of Te observed
we have plotted
with the time
at which x . 98.50 at the local
the poor
resolution
in
only when the
local
in
on 41 April
sunrise.
On 15 March
sunrise
(A Te/dt
‘t ,4).
and
- 42“/min.
to its earlier
sunrise,
level
reported24
the ionosphere
no perceptible
be attributed
during
these
points.
is
increase
to the shorter
y to the fast photoelectrons.
rneas”rements
).
At Millstone
the behavior
equinoctial
in Fig. i 9 the times
and conjugate
by the pr-esent
hour)
by as much as 4 to 5 hours.
from
and Nanca.y might
‘t8
to indicate
commenced.
before
conjugate
(-+
heating
with local
different
Figure
resolution
sunrise
However,
300 and 375 km ob-
a peak and then decline
and local
29
and about
98- to 99”)
in 1963 and 1964
sunrise.
for
heating
2 hours
local
is distinctly
together
afforded
Circle
periods
and conjugate
and local
to precede
increases
the con-
and a photoelec-
We have attempted
– that associated
vicmsly,
time
obtained
periods.
at Millstone
line lengt b for Nanc ay, with consequent
In order
30-day
with conjugate
values
between
where,
since
at
11), and it is not
~ reaches
is another abrupt increase
20-22
for Arecibo
(L by Carlson
sunrise
by the French
(i. e.,
when there
to that reported
3 October
in winter
the day (Table
these
(at - 2“/min. ) approximately
conjugate
1963,
during
which
23
at
with sunrise
only on about 30 days each equinox.
that conjugate
in ATe/dt
x
is found
of the atmosphere.
coinciding
the protonosphere,
than about two hours.
for
(as on i March
riods
by more
Hill
sunrise
distance
south of the Antarctic
coinciding
selected
expansion
is a sunrise
by averaging
these
abrupt change
begin~
sunrise
one to distinguish
allows
separated
This
field
obtained
the zenith
with
in the height
with local
at Millstone
from
lies
obtained
the onset of heating
to do so until local
soon heated
local
results
of days during
is only a single
In this case
point to Millstone
ionosphere
when the temperature
throughout
west than Mills tone,4 there
that the
the conjugate
associated
at Millstone
level
of the
has been found to coincide
to the greater
of heating
in
feature
and demonstrated
maximum,
heat conducted
at which we. estimate
the temperature
in Te.
minimum
occurring
is a regular
from
of the heating
cannot be expected
between
temperature
these measurements
are
at Arecibo,
sunspot
even at ground
the conjugate
evidence
is less – from
temperature
streaming
Heating
owing
evidence
of the temperature
electron
two sunrises
sunlit
farther
on a number
continues
increases
point which precedes
an examination
shows
Toward
The phenomenon
to distinguish
tron flux.
there
noticed
point then remains
readily
The onset
distance.
has been made for
the conjugate
in electron
months
300 to 400 km is used as an indicator.
A search
jugate
increase
980 to 99” at sunspot
=
– about 2.6
10NOSPHERE
the winter
in that hemisphere.
x
with season
at 600 km the variation
is a flux of fast photoelectrons
of
At night the peak is found
markedly
20-22 has shown that the phenomenon
behavior
at the same
heating
However,
to a predawn
Carlson
distance
to about i.6.
which varies
CONJUGATE
that time
sunrise
a solar
range
has declined
in winter.
FROM
attention
of this heating
following
Te/Ti
but has a value
and 1.6 to 1.7 in summer.
PHOTOELECTRONS
March.
altitude
altitude,
pe-
of occurrence,
As remarked
does not permit
pre the
precise
time
of the onset of heating
of uncertainty.
a zenith
distance
~ . i06-,
large
It would appear
x = 98.5-
However,
change
is reached,
a small
in the value
shift
and the bars
to be established,
that both local
and conjugate
in Fig. 19 indicate
heating
and that the true value
commence
probably
lies between
in the assumed
latitude
of the conjugate
of x at which conjugate
beating
would appear
the range
slightly
before
x . 400” and
point would make
a
to commence.
Theoretical
studies of tbe behavior of the electron
temperature
during sunrise have been
25
made by da Rosa
who finds that Te begins to increase
as x reaches ii 0“. In this analysis the
beat input to tbe electron
Bowhill
model
of midday
as the shadow
lations
nonlocal
of the earth’s
would be required
VIII.
heating
atmosphere
to estimate
to be a Chapman
26
was assumed
must be well
what effect
function
above.
above
below
This
300 km and the Geisler
seems
rather
-
arbitrary
400 km at x . 11 O“ and exact
calcu-
this must have on tbe fast photoelectron
flux.
DISCUSSION
A number
variations
of authors
Fig. i 3(c),
perature
layer
during
the period
to be supported
with foF2
daytime
for
and a minimum
either.
OBSERVING
The parameters
that tbe 23-cm
seasonal
Thus,
of tbe smaller
quency
radar.
Tbe antenna
the 68-cm
23-cm
parametric
spectral
radar
variations
The
do not seem
that definitely
the variation
~.
is small. –
in these
quantities [Figs. 45(a) and 17(a)]
17, i9 i“ Fig ~4 (by ~lmo*t
of Layer thickness
impossible
to invoke
systems
of 7db less
sensitive
(84-foot
diameter)
temperature
changes
or the reaction
the signals
are
and described
applied
applied
previously.’
is the insertion
than the 68-cm
system
employs
which re-
rates
of the
amplifying
stages,
to the IF amplifiers
to tbe signals
One change
111. lt can be seen
system.
for
This
tbe higher
aCassegrainian
in azimuth
in one position.
of a new set of crystal
would be expected
in Table
It can be driven
it &>as left
as first
are given
antenna employed
radar
pedestal.
in cascade
all the operations
width of the echoes
radar
observations
amplifiers
conversion
wavelength
is ‘300-K.
The neutral temperature
Tn is a maximum
in tbe
27
and hence variations
in Tn cannot be invoked
on a 90-foot
but in these
fi”rom this point on,
and tem-
at tbe peak of tbe
The only parameter
However,
at hmax.
used with the 23-cm
and is mounted
of 4-/see,
density
with
and winter,
of the 68- and 23-cm
is of the order
of frequency
These
in August
and i7(a)
PROCEDURE
radar
four diode
interval.
variations
it appears
a consequence
speeds
16(a),
temperature
variation
elsewhere.
in summer
chiefly
arrangement
encountered
The electron
changes of the height distribution
of the constituents
28
to explain the seasonal
anomaly.
10ss processes
23-CM
i5(a),
and at 300kn1 the decrease
part of the year.
is ‘Fe/Ti
this seasonal
of two) must be sought
sult in either
were
Figs.
of temperature
to 2.6 in winter.
of major
as an explanation
to winter
for the first
correlated
values
between
July to December
swnmer
in terms
correspondence
by about ’100“K in this height
that an explanation
solstices
to be some
decreases
by the results
The absence
frequency
from
2.4 in summer
a factor
from
anomaly
When comparing
by -200-1<
a variation
shows
does seem
the seasonal
critical
and December.
we find that there
ion temperature
from
The lowest
in November
decreases
shows
have sought to explain
of the atmosphere.
and the highest
IX.
gas was assumed
is
fre feed
and elevation
employs
and following
two stages
of the 68-cm
are the same
receiver.
as carried
out with
that must be made when operating
filters
to be approximately
in the spectrum
three
at
The receiver
times
analyzer.
wider
at
The
owing
30
. . . .._.,,... _,_.”
.=.e.#_#_
.—.
TABLE
RADAR
SYSTEMS
FOR
EMPLOYED
IONOSPHERIC
Location
Antenna
beamwidth
Polarization
Effective
Frequency
Transmitter
AT
MILLSTONE
BAC<SCATTER
71.5”W’t2.6°N
71.5 -W42,6”N
0.7”
0.6”
Circular
Circular
power
440 MHz
1295 MHz
2.5
4 MW
MW
0.1,
pulse I ength$
0.5,
40 Hz
System temperature
250° K.
heights
operating
frequency
emplo’?!d.
below .200 km wheretbe
spectral
width of the reflec
half-peak
width encountered
When used to. observe
so that the zenith
way. it is possible
to place
pied by the ground-clutter
creases
penalty
tering
volume.l
spectrum
ionosphere,
a given
a pulse
x,
thereby
angle
location
In the work
employed.
yond the ground
power
the beam,
A fu>ther
constraint
at Millstone
temperature
the range
depend
reported
This
clutter
spread
of the ionosphere,
here,
x
The choice
of pulse
powerful
radar
the pulse
the ~onstraint
reached.
with a 0.5-msec
pulse
the spectral
The
system
in
to the scatof making
(’l/r Hz) must
are required.
depend directly
by the
Finally,
upon
T
in
and
of the antenna.
length
to place
For this value
in the zenith
of
x
r . 0.5 msec
(A1I ==30 km)
the E-region
echo be-
a
6-db reduction
with the same
requirement.
to about 0.2 msec
width of the pulse
it was not possible
a radar
of the range
in Eq. (2)1 introduced
will
required
by the sensitivity
ccmld be shortened
relating
for
T (by the method
70s and pulse
the observations
was determined
~ . 70-) befOre
=
occude-
achieved.
width of the pulse
x (and bearing)
when using this pulse length.
olution.
length
measurements
was the minimum
resolution
since,
[<1 H(uto) I ‘>al.g
echoes
with ~~~
ln this”””
than the interval
as the square
is that the spectral
a zenith distance
to making
the height
upon the pulse
distance
the
to
is operated
the height Ah illumiriated
strength
falls
and composition
(The center
of 60” to 80”.
greater
length,
improving
broadening
tO
mass is higher,
the radar
of. the order
at a delay
of fixed
of the ground-clutter
zenith distance
relative
Even
Hill)
refer
8...0 to *5. OkHz. )
of the signal
imposed
upon the zenith
is encountered
system
from
the echo intensity
than the spectral
if accurate
in addition,
were
fill
less
range
and the mean ionic
by such a large: faetm.
the .ech@ Crsm the E-region
zenith
measurements
be considerably
is lower
For
db.
of the 23-cnl Obser~ atiOns
of the beam is
one must pay fo~. this is a reduction
which the scatterers
may,
inthe
di=tance
echoes.
with increasing
butsin,:emost
the E- and F1 -regions
the .e.ntenna tilted
-20
-2db
is not increased
is usually
K
foreach)
db
ion. temperature
teds ignals
continuously
db
-1
System I osses
inset
for each)
-170”
(monitored
-20
ore pcssible
40 Hz
Pulse repef”’~: n frequency
Postdetectorintegration
0.5
l. Omsec
(other values
to the higher
HILL
STUDIES
1600 mz
aperture
Peak transmitter
111
Given
(yielding
height
res-
a more
Ah s= 12 km at
to that of the medium
to obtain useful
of echo
measurement
is
at night
or near
sunrise
or sunset
when the electron
herein
apply only to daytime
erably
less
conditions.
than might be desired,
temperature
measurements
Table
IV lists
analyzer
was employed
base.
to examine
heights
than is 8chieved
spectra
TABLE
IONOSPHERE
THE
observations
at delays
reported
(Ah . 30 km is considwith the 68-cm
radar
were
made.
The spectrum
of 5.5, 2.0, 2.5, . . .5.0 msec
along
IV
OBSERVATIONS
23-CM
Thus the results
achieved
(Ah = 75 km).
in i 966 on which
the signal
is low.
resolution
but it is far better
at F2-region
the days and times
the time
concentration
The height
RADAR
USING
IN
1964
lleighf/Rcmge
Date
Crxmnenceme.t
End
Exwnined
(EST)
(EST)
16 April
I 000
1600
80-260
13 August
0900
1600
80-230
10 September
0900
1500
80-230
25 September
0900
1500
80-230
9 October
0900
1500
80-290
23 October
1200
I 530
80-230
1000
1600
80-260
0900
1630
80-260
(1 964)
5 Ncwember
20 November
(km)
__.___J
On many
days the signals
of 4.5 or 5.o msec.
shown for
amine
were
of these
to scale,
quantities
an average
over
from
useful
spectral
which signal
each position
minutes,
measurements
spectra
of the sampling
and thus it usually
4.5 to 5.0 msec,
could be obtained
on the time
required
and typically
at delays
is
base the integra-
about an hour to ex-
the entire
range
would be
day.
subsequently
in the wing to that at the center
variation
ficult
in a given
obtained
interval
For
for five
in the range
6 or 7 times
The spectra
amplitude
IV.
to proceed
all the delays
sampled
too weak to permit
Thus the height
each day in Table
tion was allowed
were
was evident,
was computed
plotted
and scaled
to yield
and f the half-peak-power
and since
for
the spectra
x and f for
the ratio
width.
were,
each height
x between
No marked
in general,
interval
weak
the
diurnal
and dif-
on any one given
day.
X.
23-CM
A.
DATA
Problem
In the height
low altitudes
possible
O;
REDUCTION
of Mixtures
interval
for
‘t 00 to 200 km,
and NO+ ions predominate,
in principle
observations
from
of Ions
to determine
mixtures
tbe compos itfon of the ionosphere
but higher
both the composition
of 0+ and H+ (OP He+)
32
ions
up 0+ is the principal
changes.
29
While
ion.
and temperature
backs catter
encountered
near
from
At
it is
radar
i 000 km6 this is not the
case
for mixtures
NO+ ions,
(that is,
of 0+,
o;
+ No;)
the relative
abundance
temperature
Ti.
ion) temperature
to make
the basis
of present
spheric
knOwl:jg:i
drag
temperature
to altitudes
is then necessary
concerning
atmosphere
or 290 km) where
to assume
only some
here
is the exponential
by the 1965 CIRA
HZ., respectively),
ing these
height
h above
In sum,
the earth
obtained
at more
and 20 November),
the agreement
than
one
it is possible
and then deduce
data obtained
by the French
to the solar
250
such an approach
which corre-.
to be present.
all lower
It
heights.
(8)
flux conditions
temperature
to 300 km.
in this height
to obtain more
group
based
the exo-
1 and 11 (~ = 65 and 75 x 10 -22 w/rn2/
the neutral
from
range
Tex
This
at the Centre
of Tex.
some
d’ Etudes
durof the
the ion
Where
9 October,
spectra
5 November
In such instances
to the procedure
dependence
has been adopted
National
is open to the objection
be fixed.
confidence
to assume
approach
By determining
will
than one estimate
encountered
Tn as a function
(16 April,
and this lent some
Te and Ti.
spectra,
Ti (= Tn) for
with only one unknown Tex.
good,
temperature
directly
on
in the in-
120)]
the Models
it may be noted that it is possible
upon altitude
However,
altitude
found was invariably
In passing,
for
most closely
in the interval
assumption,
determine
the uppermost
O.0156(h–
Eq. (8) defines
(in kilometers)
at any height
(or
dependence
exp[–
atmosphere
which correspond
observations.
temperature
were
model
in
Te and ion
are tbe same
of neutral
instance,
for
a change
and electron
acceptable
temperatures
dependence
Stated
for two of the unknown it is
Tbe most
from
from
to the heavy
temperature
composition
O;
30
following
only 0+ ions may be presumed
altitude
TN = Tex – (Tex – 355)
implied
spectrum
One may then adopt a profile
8
ion abundance
in the electron
the third.
to distinguish
the temperature.
to obtain results
as was done in the present
260,
The one that was adopted
change
and in order
of the neutral
Tex
(230,
signal
:2 that the ion and neutral
,
data or,
0+)
concerning
identical
ions by a suitable
(that is,
One can use the data tO determine
an assumption
400 to 200 km.
upon satellite
spend
Of these
in formation
an almost
but nOt all three,
necessary
from
to recover
AccOFdingly,
is it impossible
the ratiO Of the light
iOns withOut additional
it is possible
Not merely
and NO+ ions.
but one cannOt determine
otherwise,
terval
O;,
adopted.
of composition
in the reduction
of
24
des Telecommunications.
that the ion composition
has been measured
in only an extremely
limited number of rocket flights (Fig. 20).
In addition,
on theoretical
33
grounds
we would expect the composition
to exhibit diurnal changes,
and experimental
evi34
dence for this has been obtained by Istomin,
as illustrated
in Fig. 21, and Holmes,
et
.— al.35
B.
Electron
Temperature
When the ion temperature
above,
the electron
out any knowledge
the peak power
ratio
Te/Ti.6
of Ti as well
ture
range
puted for
Te
has been determined
temperature
can be estimated
of the ion composition.
This
in the wihg of the spectrum
However,
for
precise
as the composition.
400° K c Ti < i400-K
a radar
frequency
for mixtures
f . ‘1295 MHZ,
from
will
through
of, Fig. 22, somewhat
. 0.5 msec,
not be wildly
better
primarily
depends
to take into account
results
will
frequency
if a mean cur”e
be obtained
x between
upon the
value
for the tempera-
iOO% NO+ and 50% O+,
in er?or
with-
the actual
of x with Te/Ti
and plasma
outlined
spectrum
the fact that the ratio
the variation
of tOOqo 0+,
pulse
by the procedure
the shape of the signal
it is necessary
the results
regions
follows
22 shows
It can be seen that although
the shaded
from
and that in the center
results
Figure
at all altitudes
50% NO+ comfN = iO MHz.
is drawn
if some
model
33
.-—.—
,—___
..,.,
,,,,,:,,,,,,,,,,,,
,,
Fig. 20.
of 0+
Rocket
and
profiles
sum of O;
of relative
and NO+
abundance
ions by three
workers.
I
}
,m
I
o
lSTOMIN
-+-1
20
I
{!9611
1
I
40
I
I
.,
I
I
2.0
,,
PERCENT
Fig. 21.
Vciri~tion
of.abundwwe
of light-
tcrhcxwy
icmswith.
s.lar
di<fa.ce,
acc.rding
t.. Istomi”.
zenith
F
34
(wet)
lSTOMIN
,m
I
1
0
I
1
20
I
40
I
60
PERCENT
,.0
28
,,s
z.4
Fig. 22.
~
2.2
m
g
Variation
of ratio
x of prover in wing
of spectrum to that at center frequency
for three
compositions,
tion Of T~Ti
~
of
,,0
seen
%
g ,,8
ion
tempwature5
that
of
because
ion temperature
spread
ratio
least approximately
ture Ti w composition.
!,6
,.4
,.2
,,0
,,0
2.0
3.0
40
34
400
to
1400”
is not
T~Ti
I arge
canbe
irrespective
K.
as a funcand
It
range
can
be
electron-to-
determined
of ion tempera-
at
1
80
1
~,
TABLE
MODEL
V
FOR VARIATION
AND
COMPOSITION
Altitude
OF Te/Ti,
WITtI
Ti,
ALTITUDE
Te/Ti
Ti
0+
(%)
(km)
I 30
1.0
435
0
170
1.5
660
45
200
2.0
715
58
230
2.5
750
I 00
3.0
800
I 00
>270
for
the variation
Te/Ti
of Ti,
and composition
model
is not in goOd agreement
model
finally
this model
electron
adopted
a single
with the results
on the basis
curve
temperature
x and Te/Ti
height
0+
from
difficult
composition
what are
to change
thereby
initially
alter
without
follows
ence
the results
fluence
for
the values
low
that differs
support
Table
Te/Ti
to
does
the
not,
model;
in fact,
To
results
Sees. X-D
theoretical
spectra
were
2,0—
at any
,.5—
here.
s
~
o
I
that
rL,,l!>l<lc,,
,,0
that then
L>
2.0
WING-TO-CENTER
Adopted
terfreq.ency.
computed,
cent in 25-percent
steps.
(The
[Eq. (2)] with the weight
and gating
!.,
,.,,0
*.S
3,0
,
and XII-A).
a set
using
given by Fejm-5f orthefollowing
a pulse
pI
to em-
from
spectra,
i“ 200- steps,
mitting
1
variation
of Te/Ti
with
ratio
x
between power in wing of spectrum to that cd cen-
Ti = 400 to i600SK
volved
of
<
>.
It
of
assumed
the
(Table
f~om
corresp.ands to model for
Tir and compositicm with
V) which
height
is in good agreement
with
obtained.
cases:
Te/Ti.
other
This cuwe
variotion of Te/Ti,
results later
equations
Using
2.5—
~
the observed
analyze
V,
influ-
reported
significantly
Ion Composition
in Table
which all the values
/
Fig, 23.
c.
23) froin
The
3.0—
and
can be de-
it is not possible
(see
(Fig.
3.5
in Fig. 23 does in-
V and obtain
the model
may be tried.
it is
of Te ob-
of composition
however,
model
that the
with
values,
Te/T:Significantly
fn practive,
in
increase
and above
of c~rve
ploy a model
given
and the
At 230km
recourse
The choice
In the event
in 1964 is presented
that only 0+ ions are pres-
that the model
altitude.
Ti,
significantly
and thus at this altitude
termined
a revised
was drawn
the values
below about i75 km.
it has been assumed
ent,
all
the model
appreciably
tained
is adopted.
derived.
It should be noted that as Te/Tr
percentage
obtained,
of the observations
relating
were
with height
1.0 to4. O in 0.25 steps,
ion was taken to be NO+. )
function that repmssents
the radar
time
These
spectra
0+ = O to iOO perwere
then con-
the combine d(insti-u mental )effect
base a section
35
percentage
equal in length
of trans-
to the transmitted
m
CE, T,
Fig. 24.
(along
Variation
ordinate)
of spectral
Fig. 25.
ratio
Variation
Te/Ti
width
for different
(= 1. 75).
These ..wes
c..
polation given T; and f.
as a function
R-TO
-H.LF-PE.
be .sed
of spectral
fcm case of only
Ti and
0+
f.
width
and
determine
ions present.
T~Ti
for spectra
the height
230 to 290 km wereanalyzed
yielded
estimates
about 600 tO 800 km.
of neutral
value
composition
f and wing-to-center
below
thereby
of icm tempemture
fixed
Ti and electron-to-ion
above 220 km and
interval
f I,Hz1
f as a function
.ompositi.mw
of icm temperature
used to determ; ne
K WIDTH
exospheric
of T~Ti
by inter-
ratio
x
temperature
These curves can be
obtained
Spectra
for al fit.des
cbtained
in
using this chart and
temperature
Tex.
36
—
—
~LLSe,
This
ployed
function
was then convolved
in the receiver
spectrum
A set of curves
chosen
grams.
(Fig.
for
ratiO Te/TC
each case
In addition,
a chart
25) was prepared
values
for
of x and f for
the corresponding
The value
tained
observed
(e. g.,
value
the variation
the measured
D.
Checks
A number
comparison
the ratio
For
value
of tests
value
of Te/Ti
was not precisely
the values
or other
to see if tbe results
data.
delays,
As noted above,
we require
indicate
spectra,
ion temperature
so derived
with that deduced
should be expected.
Further,
why ratios
of f and Ti inserted.
in the approach
the method
of analysis.
with values
A.
compare
these
VI where
adopted,
radar
values
satellite
determines
the
and by interpolat-
+ NO+] are found.
as on any chart,
from
adjacent
are reasonable,
In
and it was
charts.
quite apart from
when it has been possible
outlined
above.
value.
if reasonable
because
compositions
sensible
on different
values
obtained
are
Next,
and compare
(Fig.
in no way forced
to result
200-km
is no
by the values
one derives
above
the
differences
23) there
are obtained,
days) with the 68-cm
Tex
Failure
altitude.
No large
to obtain the composition
any
to deduce
the same
of NO+ ions at 230-km
in the manner
altitude
from
may be com-
vertically
directed
radar.
Tex,
it is instructive
Tex
spanning
the two sets
of values
The satellite
Observatory
are
are on average
values
9 percent),
to determine
satellite
kindly furnished
givem
The latter
some
which seems
40-K
(i. e.,
5 percent)
37
is done
higher
valws
of
of the seven-
of Millstone.
they are not in violent
as 11
true, !, then the radar
larger
This
to
by Dr. L. G. Jacchia
are averages
the latitude
good agreement,
are regarded
drag observations.
of Tex
0900 to 1500 EST for
do not show strikingly
values
from
determinations
the time period
If the satellite
of 71 “K (i. e.,
of the experiment
with ones obtained
drag
the Smiths onian Astrophysical
error
of [O;
that only NO+ ions are present,
the temperatures
(albeit
Temperature
hour values
ment.
obtained
ob-
A point representing
on this chart,
deduced
tempera-
is obtained.
Te/Tiis
than ‘f 00% NO+ (or 0+) should not be required
words,
it is not the main objective
in Table
values.
neutral
at
RESULTS
Exospheric
While
assuming
of more
Fi&Ry,
obtained
number
when interpolating
In other
confidence
23-CM
Ti and Te/Ti
Next,
of Te/Ti
that they should each give
a significant
the lowest
XI.
Eq. (8).
dia-
25) and the
than one value
the same
of composition
compo-
of x and f
(Fig.
altitude),
is selected.
of Ti is then entered
we may examine
pared
from
of 0+ ions and percentage
can be applied
at different
reason
this chart
The value
value
the five
of Ti the exospheric
is then obtained
f as a func-
on Results
to do so would most likely
a priori
em-
of one of these
as a function
260 - and 290-km
x, using Fig. 23.
width
representing
an example
Using
each value
to the measured
between
with rocket
spectra
curves
of Ti and Te/Ti
(230-,
altitudes
the percentage
to interpolate
five
24 represents
Eq. (8) and a mean is taken when more
of f arid the deduced
most cases
necessary
spectra
are determined.
from
of the filters
of the spectral
of only 0+ ions present.
Fig. 24) closest
the curves
were
showing
from
for each altitude
there
Figure
the case
heights
ing between
from
In all,
the variation
of Te/Ti.
of Ti (= Tn) at all lower
which chart
showing
the uppermost
is determined
ture Tex
function
analyzer.
was next prepared
tion of Ti fOr a given
~ition~
[Eq. (1)] with the spectral
Although
disagree.
than the radar
exhibit
than we would have anticipated
an RMS
(Sec. XII).
,“,
TABLE
VALUES
OBTAINED
AVERAGED
FOR
OVER
Vi
EXOSPHERIC
THE TIME
TEMPERATURE
INTERVAL
0900
TO
T
1500
,
ET
Difference
Satellite
Radar
Satellite
Minus
Tex(OK)
16 April
788
865.
77
13 August
759
790
31
10 September
897
815
25 September
807
855
48
9 October
794
890
96
23 Octcber
848
825
5 November
800
880
80
20 November
726
820
94
~K)
–82
-23
Meon
B.
Electron
The lowest
centered
ing from
altitude
group 24 over
bistatic
radar
system
some
are
from
poor
together
by the exploring
tember
flects
of points
since
values,
were
to draw
e.g.,
in Figs.
smooth
EST)
bars.
curves
for the ion temperature
through
the measurement
has been interpreted
in Figs.
range
to compute
resolution
colli-
(-30 km)
[-3 km).
each month the results
obtained
26(a-e)
tbe two sets
during
denote
of points
there
near
have
the same month,
the height
with little
is a difference
220 km.
made at 68 cm (beam
down into regions
on the assumption
after
not included
be noted that with the exception
that is largest
by the
than one day) and h~ve been plotted,
and November,
the pulse is long enough to extend
yet tbe spectrum
observations
For
scatter-
that are about a
processes
the height
no
the CNET
in this altitude
frequencies
temperatures
It will
October
more
employing
has been made
26(a-e).
for
The bars
[Sec. IV).
September,
in the French
showed
Of TbOmson
that other
in this work because
available
and are not error
perhaps
No attempt
range.
obtained
collision
a region
altitude)
have been reported
workers,
frequency
was<or
(i07-km
findings
These
yield
indicating
[0900 to i500
tbe fact that at this altitude
estimate,
ent,
pulse
instances,
the two sets
40
characteristic
Similar
results
are presented
radar
peak,
the collision
Their
with that achieved
observations
directed
it is possible
In several
=
could be obtained
of 2. Onlsec
90 to ii O km.
in this altitude
tbe spectra
with the mean daytime
with the vertically
had a sin:f
important.
interval
profile.
results
(where
at a delay
able to estimate
compared
The temperature
been averaged
are
than accepted
important
sion frequencies
is extremely
were
temperature
of two bigher
in the theory
but instead
the height
temperature
obtained
when collisions
French
factor
to which the electron
The spectrum
appearance,
a plasma
assuming
Difference
Temperature
at !36 km.
double-humped
Radar
Tex(OK)
Date
where
This
vertical)
O;
occupied
of Sep-
difficulty.
between
probably
re-
is an under-
and NO+ are pres-
that only 0+ ions are present.
38
..—. .. ..—____
:
(a) April
:
i,
.
1964.
TEMPERATURE
(°Kl
@) August 1964.
~
(c) September
1964.
:
r,
r
,, MPEFI.TuREl-K]
Fig. 26.
Average
daytime
(O?OOtO 1500 hmm)
temperature
39
curves obtained
with
23-and
68-cm
systems
600$
NOVEMBER,’3.4
C.VFFAGE DLY, IME
50C -
:
+00 –
:
.
i,
‘
300 –
200
:)
,00.
1
I
I
moo
400
TEMPERATURE
(d)
On the basis
of the results
in Figs.
The resolution
flights.
acceptance
solar
26(a-e)
mechanism
1964.
we may say that at temperate
is able selectively
great
latitudes
Te > T.
by recent
Te > Ti for
theoretical
great
dip angle
heights
altitude
trons
field
will
at high temperate
(Fig.
amOunts Of
or that Some other
of about 300 to 350 km, above which Ti > Tn.
31,32
of Banks.
Our results do not extend
whether
Te/Ti
-
1.0 at about 4000km
reported
in previous
papers
as assumed by
2-4
suggest that
and J30whill) will
by the electrons
is sufficiently
remain
below
latitudes,
large,
be to transport
via Coulomb
beat downwards
encounters.
so that the heat conductivity
that of the electrons
at all altitudes.
we may expect
that the temperatures
31 32
but Te > Ti > Tn.
‘
Where
is great
Thus,
the
enough,
above
‘t 000-km
of the neutrals,
elec-
Ion Composition
The results
together
lar~e
heights
since
estimates
Geisler,
and ions are all isothermal,
C.
interest,
range of heights above the F-region,
and this too is supported
3i
Banks
has shown that the effect of thermal conduction through
by Hanson,
of the earth’s
that etiremely
at E-region
38
altitudes.
at these
The results
that bas been supplied
the ion temperature
with considerable
a large
studies.
the ion gas (neglected
from
to det~-mine
is awaited
one to conclude
to heat electrons
and Bowhill.
but that below
are absorbed
with theoretical
heights
and Geisler
at this latitude
forces
that Ti = Tn up to an altitude
is in good agreement
to sufficiently
the daytime,
of this disagreement
– 106 eV/cm2/see)
(-i05
It also appears
Hansm3’
during
of the rocket’determination
EIJV energy
This
i35km
?,.
i20km it would ap?e~r
24
from Thorns on
that Te . Tr
This is in agreement
with results reported
by Carru,
et
——al.,
37
and others from
scatter observations,
but contrary to the conclusion
reached by Spencer, e~ @.,
rocket
above
2200
Continued,
Fig. 26,
(and Tn) at all altitudes
“’’’’”c’
[W)
(e) November
1964.
Rw
1
,600
1
TEMPERATURE
[°K1
Octcber
1
for the distribution
with their
20) reported
comes
closest
above
180 km.
mean curve.
by lstomin,34
to the results
Below
that this discrepancy
These
Taylor
results
ions on the eight
may be compared
and Brinton,29
Holmes,
~
days are shown
with rocket
&.35
in Fig. 27
determinations
The mean curve
of Fig. 27
of Holmes,
this altitude
indicates
of the principal
et al. 35 (Fig. 20) and indeed the agreement
is quite good
—.
the radar results indicate fewer heavy ions.
It is possible
that tbe form
of the temperature
profile
adopted
[Eq. (8)] is in
40
—
error,
If this is the case,
the temperature
must
than given
by
have
reported
been
on average
Eq. (8).
determinations
then we find that st i 67 km
similar
findings
37 in rocket
et al.,
by Spencer,
of neutral
higher
be - 90-K
Somewhat
temperature.
These
m
indi-
.
0
cate that Tn increases
than the Harris
and then less
XII.
rapidly
DISCUSSION
A.
model
above
OF
sOmewhat
faster
+
.9
. 23
.5
A 20
—
km
60 to i70
up to ‘t
this altitude.
2 3-CM
APR
A“ G
$0 SE P
25 SEP
OCT
OCT
NO.
NOV
MEAN
I
RESULTS
Accuracy
The agreement
drag
with altitude
-Priester
IS
,3
between
determinations
spheric
of
temperature
BY averaging
has
the data
the radar
and satellite
the neutral
particle
been examined
over
the whole
exo-
in Sec. Xl.
L&LJ...l
..;J
+++
day we have
PERCENT
sought
ment,
to minimize
tbe random
yet it remains
tra that give
estimate
rise
are
the poorest.
can be made of the accuracy
that individual
estimate,
from
since
it assumes
The largest
uncertainty
from
230 to 290 km.
tial analyzer
one orbit
mounted
during
then we should expect
measuring
yield
values
closer
of Tex
There
are,
are
a number
ones.
ues are smaller
5 percent
possible
source
Tex
made by
markedly,
only on ob-
values
may be indicative
of
altitude.
by which the data could be analyzed
the satellite
a difficulty:
values
some
and this would require
width of the signals.
if this were
of error
ones,
above
yet the fact that the satellite
than the radar
imposes
for
at 26o or 290 km would
VI than those that depend
One would be to accept
radar
would differ
and NO+ ions at 230-km
schemes
20)
poten-
as 18 percent
and NO+ exist
temperature
observations
out,
(Fig.
have been published
of O;
respectively,
is borne
higher
immediately
the spectral
be obtained
and results
in the in-
determinations
40
a retarding
measurements,
amounts
include
in Table
of O;
alternative
than the corresponding
has been taken from
listed
expectations
(5 percent)
however,
io” than 0+ to match
A second
values
of possible
an ?)nder -
or NO+ ions at heights
of the exospheric
26o, and 290 km,
this difficulty.
This,
ture could no longer
This
n“rnber
suggests
determinations
+ NO+ ions was found to be as large
If substantial
of Tex which
of these
on the ,average,
which rnigbt overcome
lighter
Neither
of a small
of the radar
of O;
at 23o,
to the satellite
This
temperature
of the rocket
direct
was employed
i“ i962.
that those estimates
at 230 km.
the presence
satellite
of O;
with some
recent
to find that estimates
tbe ion temp~rature
values
servations
In the most
time
day.
radar results.
and is almcmt certainly
and the electron
absence
is in agreement
on an oriented
On a given
values
than *IO percent
of the complete
This
from 23-cm
variation.
which the percentage
or alternatively,
ti tude obtained
in both the composition
at 210 km at 1700 hours l~cal
20o km,
to better
with others.
Fig. 27.
Relative
abundance
of 0+ ions and
s.m of Oi and NO+ ions as Q function of a[-
of the individual
no diurnal
by the assumption
and in disagreement
sPec -
A crude
in determining
the spread
are accurate
values
is introduced
of measure-
true that the uppermost
to Tex
the ion temperature
terval
errors
In short,
of Tex
instead
of the satellite
the presence
a self consistent
val-
of a
pic-
done,
is the assumption
the 1965 rJIRA model
atmosphere
of an ion temperature
and is therefore
profile
ultimately
[Eq, (8)].
based
,.,,-
..m—
upon an integration
remains
of the time-dependent
in hydrostatic
invariant
boundary
upon atmospheric
included,
equilibrium,
conditions
the day.
does not allow
Attempts
but thus far no solution
permitted,
ever,
difference
(Harris-Priester
model)
of existing
B.
E-Region
The
electron
since
neutral
temperature
to tbe true value
[= kte/4rNe2]i/2
were
computed
may
indeed be larger.
factor
E-Region
dimensions
VoDand44
section
around
further
is
finds,
a one-dimensional
(an E-W
of” Te/Ti
Seasonal
Many authors
pheric
constituents
season
and/or
frequency
how-
solution
the equator).
45
elsewhere.
f~om
temperature
independent
of height
the
Moorcroftb
T:
that is re-
the Debye
length
in the altitude
D
~ange
of 3 to 4 and that the true elec-
than the values
results,
adopted,
whereas
2.5 to 5.0 MHz.
with altitude,
of the order
higher
procedure
fN = t OMHz,
of tbe electron
to the 68-cm
from
where
given
in Figs.
26(a-e).
at the highest altitudes
\,
the lowest
The effect
height
is in thermal
spectrum,
of neutral
group
higher)
equilibrium
the pulse
collisions,
occupies
evident
it
upon
of collisions
by
a height
in the next lower
only up to an altitude
the effect
rests
and is in no way altered
fn this measurement
by the French
one scale
of 140 km.
We ex-
should be quite negli-
in Composition
Variation
have suggested
ceases
the sunspot
of neutral
local
40 percent
and XII-B.
has been observed
pect that by 122 km (i. e.,
36
gible.
by the analysis
lay in the range
that is largely
derived
i 22 to 152 km.
of roughly
a plasma
about i 30 km tbe E-region
interval
other way during
in three
Equilibrium
of Sees. XII-A
numbers
by the heat42-44
of the winds set up,
range.
for
Since Te and N increase
has been applied
the considerations
creased
is
that must be generated
are discussed
to an estimate
(- 0.6 cm)
that below
the value
for
that o! (= h/4!TD) has a value
Thermal
The conclusion
D.
solution
that is dependent
of the atmosphere
tbe magnitude
profile
models
examined
leads
are approximately
correction
measurement,
bebavior
this altitude
the temperature
Te via Eq. (3).
has a value
tron temperatures
extrapolating
velocity
in which motion
over
temperature
at the heights
It follows
This
C.
motions
is known to be underestimated
spectra
density
under study.
profile
and a two-dimensional
has shown that this type of error
lated
and Pries
way the dynamical
has appeared,
between
an atmosphere
that always
44
ter,
This model assumes
Temperature
the theoretical
actual plasma
by Harris
for
of ‘t 20 km and a vertical
for horizontal
the temperature
The limitations
equation
have been made to compute
to the problem
which yields
a significant
performed
at an altitude
In this simplified
heating.
yet the model
ing during
heat conduction
that the height
to be effective
cycle.
For
example,
N2 molecules
summer
at which turbulent
mixing
of the neutral
atmos -
the height of the turbopause ) may change with
46
47
and King
have proposed
that inWright
(i. e.,
at F-region
and are responsible
heights
for
are brought
the seasonal
about in this or some
anomaly
in F2
ionization
(Sec. VI).
The presence
the solar
of additional
N2 molecules
EUV to be used in generating
significantly
via the charge
to the total
exchange
ion content.
reaction
N:
at F-region
ions,
heights
which rapidly
In addition,
[Eqs. (6) and (7 )],
they will
wiD cause
recombine
increase
a larger
fraction
of
and do not contribute
the rate
of Ioss
of 0+ ions
which is thought to be the principal
loss
42
———
—_-
—
.,.,,.,.__. .,-”._ ....
28.
Fig.
Results shown in Fig. 27 have here been
repl otted
when averaged
is o tendency
persist
during
to higher
scmal changes
turn
linked
tration
little
neutral
composition,
seasonal
anomaly
reflect
which
in
tO
seaore
electron
in
concen-
Since at this latitude the height of the peak of the F2 region
.
that we should expect a greater
at sunspot minimum,%v Lt follows
shows
in the F-region.
seasonal
variation
Accordingly,
just below
we have averaged
thcm in Fig. 28.
On the basis
greater
during
xIII.
There
and NO+
This may
dance of NO+ ions at altitudes
altitudes
theory.
02
13(c)l.
[Fig.
mechanism
altitudes.
in
to
over three s:asons.
summer for
We caution,
the F2 peak
the results
however,
than during
that Fig.
if the explanation
shown in Fig. 27 into three
of this figure,
summer
(- 230 km),
it does
appear
winter
or equinox,
28 is based
seasons
that NO+ and O;
lending
upon an extremely
abun-
is correct.
and replotted
ions persist
some
support
limited
sample
to
for
this
of data.
SLIMMARY
A.
Daytime
Electron
The midday
temperate
about 400 km.
total electron
of Nmax F2 are about twice
values
latitudes
at sunspot
At these
content
at the equinoxes,
Densities
minimum.
altitudes
observed,
the density
for
with the summer
of the F-region
(measured
This
by almost
variation
in winter
by Faraday
being
than the winter
above
As a result,
measurements
is a maximum
at north
in the densities
at the equinoxes.
rotation
deeper
any criterion)
as in midsummer
is not reflected
is a maximum
example,
minimum
as large
one.
the
is a maximum
The “ thickness”
in summer
and minimum
in
\vinter.
The pattern
of behavior
seems unrelated to seasonal variations
of the electron,
ion or neu27
We are forced to suppose that the seasonal anomaly is the result of in46,47
48
rates in summer,
Some support frnm agreement
with many other workers.
tral temperatures.
creased
loss
this conclusion
radar.
These
is provided
results
may overestimate
by composition
(Fig.
tbe 0+ abundance
and O;
ions present
nations
of exospheric
temperatures.
small
in the neutral
sample
agreement
at all heights
composition
if,
with rocket
in fact,
by the difference
At altitudes
abundance
at low altitudes
determinations
in fair
at 230 km as suggested
sonal “ariat ion in the relative
changes
27) are
above
at these
of data a“d should be treated
altitudes.
there
is a small
in the satellite
about i70 km,
of 0+ (minirnmn
in summer)
However,
using the 23-cm
determinations
(Fig.
20),
percentage
and radar
the results
of NO+
determi-
suggest
that may be related
this conclusion
rests
but
a sew
to
upon a
with caution.
43
—=>”,...
—.,..
hmax is a minimum
In all seasons,
quently
scale
rises
to reach
height
B.
Nighttime
In summer
number
Electron
midnight.
is accomplished
ground sunrise
and subse-
About half of this rise
during
(i. e.,
one
the daytime.
Densities
and equinoctial
months
the electron
density
decreases
throughout
the night.
A
have attempted to derive
ionospheric
loss rates, e. g., from the cbserved
de49
50
or
from
eclipse
results.
These
have
often
yielded
conflicting
results
at night
51
The latter are usually much higher than valdisagree
with laboratory
values.
cay of the layer
in turn,
ues deduced
from
the behavior
ture on the question
minimum,
the ionization
the supply
of electrons
solved
appears
or increases
to maintain
the apparent
to equal
F-Payer.
rise
52.55
to a considerable
It appears
during the night and the subseq~ent
required
enough to reduce
and this has given
of the nighttime
of the .protono$phere
in ~he tube of force
large
constant
problem
of the F-region
of the maintenance
the cooling
of electrons
bydrostatyc
loss
rates
or even exceed
.fo.r a considerable
bya
pel-iod
redistribution
equilibrium
can supply
considerable
the loss
litera-
that at sunspot
factor.
of
a flux
In winter
so that the density
either
re-
It shcmld be note”d” that the
of the night.
of a tube of force that was investig.atedby
Geislet
and Bowhtil!.5 has been
46
by Gliddon
on the assumption .that the electron
de.nslties at all altitudes d.o
of the-cooling
rigorously
not change.
In actuality;
altitudes and
this,
the lowering
in turn,
ing of the protonosphere
cated
(- 290 km) near
constikcent)
after
of authors
which,
mains
a maximum
of the ionizable
2 to 3 hours
(- 200 km)
one which still
will
of the temperature
serve
to convect
and the redistribution
awaits
a rigorous
will
cause
heat downward.
of. the ionization
electrons
Thus,
to diffuse ‘to lower
the problem.
that this
.sf the cool-
produ ties is a compli-
solution.
,.
C.
Daytime
Using
analyzed
heights
13kctrcm
the exponential
23-cm
(below
this altitude
to 800 km.
radar
{30 km] thermal
There
The daytime
in a region
of the order
through
below
vate
made on eight days in i 964.
between
measurements
Ti becomes
is little
in the i 965 CIRA
greater
seasonal
electrons
atmosphere,
We infer
than the neutral
variation
(at least
that at E-region
and ions prevails,
show that this inequality
exospheric
at sunspot
we hav,e
but that above
persists,
at least
temperature
above
minimum)
up
in the tempera-
obtained.
electron
has been predicted,
that theory
law employed
equilibrium
The 68-cm
In addition,
about 300 km,
i. e.,
temperature
measurements
Te > Ti.
ture profiles
Temperatures
temperatures
and above
that should be isothermal
and observation
can largely
of 6 x + 09 eV/cm2/sec
the 500. km level
communication)
process
e + 0(3PJ)
If this is so,
than supposed.
-
the cooling
This
according
be reconciled
of -5 x 308/cm2/sec
rise
This
for
the electrons,
at all altitudes,
56
we have suggested
Elsewhere
if there
is a deposition
might be produced
which deposit
may be seriously
namely,
of heat above
500 km
by a flux of photoelectrons
A. Dalgarno
theory
up to 300 km than
in Te persists
to theory.
(in winter),
that existing
with altitude
gradient
in the protonosphere.
have postulated
cooling
rapid
a temperature
in winter.
i 000 km and 4.25 eV/cm2/sec
ing an important
show a less
this altitude
1.75 X ‘109 eV/cm2/sec
and T. P, Degges
in error
(pri-
by neglect-
the reaction
e + 0(3 PJ, )
rates
would probably
(9)
at low altitudes
change
(where
the amount
oxygen
is abundant)
of heat transferred
will
locally
be higher
from
the
44
,,. ...”.
._=.. _.e____
!
I
!
to the neutrals
electrons
\
cerning
ionospheric
The temperatur~
rise
in turn,
redistribution
values
during
large
above
exhibit
only
a dramatic
tO heat supplied
throughout
from2109..to
by the
Iarge!
aft en ~sunset,
change
the F-layer
the conclusion
(above)
con-
variation,
being
of heat
at sunset,
in summer
which
and supplies
stored
conductivity
but as Te falls
and less.
least
the beat flux
tbe thermal
distance
of x = 102 * 5”.
in an expansion
happens
in the mean daytime
the protonosphere
0300 hours,
reservoir
and results
zenith
of the F-1ayer
and causes
a rapid
peak.
changes
from
at a solar
The reverse
the winter .night,
Because
to a much smaller
rapid,
rates.
seasonal
to dissipate:””
immediately
“choked-off”
the heat loss
are no major
the period
hours
at dawn is especially
Temperature
ionosphere
is maintained
eral
to cOmmence
Electron
is attributed
conjugate
not significantly
heat som-ce.
appears
of the electrons
Whtle there
nighttime
heating
lowers
Nighttime
D.
This
probably
tb.e freed for. an exospheric
Local
which,
but will
of Te and Ti,
and greateat
continue~
to be warmed
of magnitude
protcnmspbere
variesat
varying
value.
smaller
which
Te 5/2 , the heat
and
‘:
takes
sev-
flux
is quite
.‘
ACKNOWLEDGMENT
The authorwoulci
like to acknowledge
many members
of the staff of the Millstone
Hill Ra8ar
Observatory
for maintaining.
and operating
the ionospheric
radar,
rmd in particular,
W. A. Reid and J. H. McNally.
J. H. .MacLeod,
J. “Upharn and ~~~
Miss D. Tcmrigny were responsible
for the largest
part of. the data reduction,
and
the computed signal spectra
from
MIS. V. Mason and W. Mason kindly provided
which electron
and ion temperatures
could be obtained by comparison
with obkindly supplied tbe values of exospheric
temperaserved ones.
Dr. L. G. ]a.cbia
ture obtained
by satellite
orbital
decay observations
(Table VI). The author is
also gratehd
to the encouragement
of P B. Sebring and the late V. C. Pineo, and to
S. A. Sowbill for ,many stimulating
discussions.
45
by the
In summer
at the foot of tb:5f ~61d l“ine. the heat supply
rapidly
the
in winter.
heat, by conduction.
is an order
in the
values
is
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1,
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MI. T. (24 July 1962), DDC 292730.
See also, J. V. Evans
and M. Loewenthal,
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G. R. Thomas
14.
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19.
i.. Thomas,
~,
20.
H. C. carlson,
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H. Carru,
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Ed
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Phys.
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4107 (1966).
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1966), p. 249.
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Res.
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J. Frihagen,
Ed
2587 (1961).
63 (1963).
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556 (1965).
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H. Kohl and].
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J,W.
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G, A.M.
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56.
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Geisler,
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Terr,
Phys. ~0,
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Stomehocker,
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Sot.
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157 (1960).
Sci.
U,
65 (1965).
Res.
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Sci. ~,
Planet,
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81 (1967).
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anti ExOSp~,
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Ed, by W, S. Newman
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29,
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Press,
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REPORT
TITLE
Millstone
L
Hill Thomson
DESCRIPTIVE
NOTES
Technical
3,
AU TMORC51
(J-’JSt
Evans,
5.
REPOMT
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la.
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Results
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date+
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ABSTRACT
Thomson scatter
(incoherent
backscatter)
observations
of the ionosphere
were made at
Millstone
Hill at a wavelength
of 68 cm during 1964, for 30-hour periods every two weeks.
These data have been employed to derive the mean hourly F-region
(200 m 700 km) electron
density profile and electron
and ion temperature
curves in each month,
The results
are presented in this report,
together
with rhe derived seasonal
variar ion of elecrron density (at 0600,
1200, 1800 and 2400 hours local time) and the average day~b,~e (0900 to 1500) and nighttime
(2100 to 0300) electron
and ion temperature
behavior.
Separate
measurements
with a 23-cm radar permitmd
the temperature
results
reported
m be extended to lower altitudes
(-130 km) and, in addition,
provided information
concerning
the ionic constituents
between 130 and 230km.
Although 1964 was at sunspot minimum,
the seasonal
variation
in foF2 was quite evident.
k is shown that rbis feature is strictly
associated
with the peak of the layer and that densities
above 400-km altirude are highest at the equinoxes.
No seosonal
variations
of temperature
At night the peak denare found which might be large enough to account for the phenomenon.
sities are highest in summer,
and the te.lperatures
at all altitudes
highest in winter.
This
last effecr is believed largely due m heat conducted from the protono sphere,
which in winter
continues
to be heated by photoelectron
escape from the conjugate
ionosphere
which remains
sunlit throughout
the night.
,.
KEY
WORDS
Millstone
scattering
48
radar
DEcLAsSIFIED
Security
Classification
may
be