Ionic composition above F layer maximum from Ariel I satellite ion mass spectromete

Boyd, R. L. F.

Laflin, S.

Raitt, R. J.

English

NASA Technical Reports Server

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A SYNOPTIC VIEW OF IONIC CONSTITUTION ABOVE
THE F-LAYER MAXIMUM*
.
; W.J. RAITT, SUSAN LAFLIN AND R. L. F. BOYD,
__ The VK-US satellite Ariel carried an ion mass spectrometer operating on the principle of
." analysis of arriwd energy of the ions. A very large amount of data has been gathere(l and it i_
now possible to obtain a picture of the variation of the ionic composition al)ove 400 km with
latitude and longitude.
A strong diurnal effect is evident together with marked geomagnetic control. There is
evidence also for a season'd variation.
INTRODUCTION The energy of arrival of an ion depends prin-
c;pally on its mass so th'tt the energy spectrum
The international satellite Ariel I (1962 - ) consists of a number of peaks corresponding to
provided an opportunity for a synoptic study of ions of mass 16 (oxygen), 4 (helium) or 1 (hydro-
the composition of the topside ionosphere over a
prolonged period, z Data on ionic constitution gen) a.m.u. The integration of these peaks leads
to the concentration of each type of ion. Sincewas received at stations of the Minitrack network
the first derivative of the current voltage curve
from 26 April, 1962 until 26 September, 1962--a which corresponds to this integral of the energy
period of 151 days during summer in the northern distribution was one of the telemetered quantities,
hemisphere. The relative concentration of oxy- typical raw data of the kind shown in figure Igen ,n the topside ionosphere is found to increase
with latitude during the day. A marked diurnal was obtained. The sizes of the steps in these
variation in composition is also evident. This _0....
paper presents some of these data and draws
special attention to the evidence for a geomag- ""
composition fi'om a set of "_-'_.'_.---._..netic control of the
satellite passes with apogee over the equator and
another set with apogee at northern apex.
The apparatus consisted of a gridded probe _ 50 _
10 cm. in diameter. The probe was mounted on _ .'_t'-'..'_'_'"the axis of the satellite and being spherically
symmetrical was insensitive to the spin of the _ _\" "
Io%°%o ee • o• ea •
vehicle. _ .,,,, .
An ion retarding (positive sawtooth) voltage 8 I .- ........40 • • • coo •
enabled a Dryvesteyn analysis of the energy ,_ He c ....
distribution of the ions arriving to be obtained, I
the necessary double differentiation of the Icurrent-voltage characteristic being carried outelectronically. 30 I I 1 1 i 1
0 10 20 30 40 50 60 /0
*This paper was contributed to Goddard 8pace Flight Center under
the joint United Kingdom-United States program which developed DATASEQUENCENUMS[P
and launche,_ ,m satellite Ariel I.
tThe authora are affiliated with the Department of Physics, Univer- FIf;,URE 1.--Example of raw telemetered data ahowing
alty College, London, England. presence of 3 ion types.408
[
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1966028656-435
https://ntrs.nasa.gov/search.jsp?R=19660028669 2020-03-11T17:51:38+00:00Z
g_ _ _ __ . _,. ,.1_h,._., Av,*_.c.*_f__'_-_
l "IONOSPItERE AND RADIO PHYSICS " 40"
i curves lead directly to the concentrations of the '_[
'r various ion species. :! f.,_._,. , ___.,! ._.
THE DALLYVARIATION OF IONIC _ ,
CONSTITUTION
regionA umber of satellite passes over the equatorialto over _i i f5,_.__/: ' ,!::i_.]_ ._l
10°S. 10°N. and the latitude band
35°N. to 45°S. covering a period of 125 days
, in the northern summer have been analysed, to
obtain the diurnal variation in the ion transition IOXYGEN--"_L'UM:"*m'"ON,:_:_ "_:_ [
altitudes (i.e. where O+ and He + concentrations 20oI- ,3_oN . ,son I
': are equal and where He + and n + concentrations JHEUUM--HYO_OGENTRANS,T,ON_,_S - _N I
0 L I J i I l I I I 1 I I
are equal). Inevitably some seasonal and secular ,80 ,4o :00 6o 20o 2o 6o ,_ ,,o ,80 ,_o ,0o
: variations are also involved. To reduce the _ ,EFO_ENOON . AFTE_NOON _ BEFORENOONSOLAR ZENI'TH NGLE (o) .
former the altitudes are plotted as a function of FmVRE2.--Diurnal variation of transition 'fltitudes.
: solar zenith angle before and after mid-day. In
; addition, since the basic data gives composition
at the actual altitude and local solar time given to study the region between 45°N. and 45°S.
_ by the orbital parameters some processing of the during the period 12.00 to 18.00 hours over which
as the previous section shows, the diurnal varia-data is necessary in order to obtain a single para-
meter (such as transition altitude) to characterise tion is slowest. At the same time, the altitude
_ the state of ionic composition. For this purpose range does not change by more than 200 Km.
it has been assumed that ion temperature is equal Figure 3 shows contours of percentage oxygen ion
'_ concentration betweeen days 189 to 193 in 1962.
._' to gas temperature and that the composition at
one height may be obtained from that at another There is evidence for a pronounced latitude
variation in composition showing higher con-height from the hydrostatic equation. Tim gas
eentrations of oxygen ions at high latitudes.
'_ temperature function employed was based on
• the data of Harris and Priester 2 corrected to the (The change of composition from 10 percent
mean solar 10 cm. emission for the period covered [[0+] 1) ([0 ”$' by the data. O+k i:i_]= to 80 percent O_ [He-+_- 4
It is certain that this operation introduces some
error in scale but it cannot seriously affect the exceeds the composition change that might be
:: attributed to the 100 Km change in altitude by;:. general form of the results.
The diurnal variation of transition altitudes is a factor of 10). The altitude and local solar time
• plotted for the two latitude ranges in figure 2. are plotted at the side of the figure.
In addition to the evident geomagnetic control
_ (The latitude variation will be considered in more
detail in the next section). It shows a fiat maxi- of the composition there seems also to be a dis-
placement of the centre of symmetry towardsmum at solar zenith angles corresponding to
about 17.00 hours, the winter (southern) hemisphere.
LATITUDE VARIATION OF IONIC LONGITUDE VARIATION OF IONIC
CONSTITUTION CONSTITUTION
In seeking to establish the variation of compost- A variation of composition with longitude is
tion with latitude it is difficult to eliminate the likely to be due to the asymmetry of the geo-
effects of changing altitude and local solar time. magnetic field. This fact is confirmed by the way
By selecting a short period (four days) during the contours on figure 3 follow the geomagnetic
which apogee was nearly over the equator and equator.
the desc_,_ding equatorial passage occurred at Figure 4 shows similar data obtained over-the
about 1500 hours local solar time it is possible period from day 150 to day 155 in 1962. In this
1966028656-437
410 " PUBLICATIONS OF GSFC, 1964: I. SPACE SCIENCES
16 30 45
I0 "900
I I -I000J2
I] _1100
_ 14
A
_ZO0
,;uO
IO00
18,
19- 900
?,: ,oo
Fmua_'. 4.--Ion corapc&tlon contours days 151-155, 1962.
case, the effects of altitude and local solar time uncertainty and it is again evident that there is a
on the latitude variation are too great to enable strong geomagnetic control with an extremely
useful conclusions about latitude variation to be compiex situation over the South American anom-
drawn. However,variation along any single line aly. This area of increased oxygen was not
of latitude does not suffer from this source of detected on the earlier results (days 189-193)
1966028656-438
gL_
I IONOSPtlERE AND RADIO PIIYSICS 411
possibly because less data was analysed then and that where the ionic composition ratio is deter-
also thealtitudeand local,i,ne is thisregionwere mined I)y the hydrostaticequation it is the ion
:, such that the percentage oxygen was only of the temperatures, not the electron temperatures that
! order of 10 percent which is near the limit of are relevant. Effects of the magnitdde of _,hose
:_ detection of the probe. On the other hand, there illustrated could be produced by an ion tempcr-
:_ may be a real seasonal or secular difference, ature change of about 20 percent.
_._ It seems likely that many of the features may REFERENCES
be attributed to the dependence of ion tempera-
_ ture on electron concentration a while near the 1. P. J. Bowz.u, R. L. F. BoYD, W. J. RAITTand A. P.
_'_: equator the horizontal magnetic field (and pos- W_LLMOa_-,l'roc. Roy. Soe., (1964) (In press).; 2. I. tIARats and W. PRIZ._TZa. NASA Tech. Note
sibly electric fields) probably make the hydro- D-1444 (1962).
:_ static equation inapplicable. It is worth noting 3. R. L. F. BoYv and W. J. RAITT. Space Research V.
.Z
.}
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2
1966028656-439


A synoptic view of ionic constitution above the F-layer maximum

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