To study the solar control on electron density (N sub e) in the equatorial D region, a program was initiated with Soviet collaboration in 1979. A total of 31 rockets were launched during the high solar activity period, and 47 rockets during the low solar activity period, from Thumba to measure the N sub e profiles. Analysis of the data shows that the average values of N sub e for the high solar activity period are higher by a factor of about 2 to 3 compared to the low solar activity values. It was found that a single nitric oxide density, (NO), profile cannot reproduce all the observed N sub e profiles. An attempt was made to reproduce theoretically the observed N sub e profiles by introducing variation in (NO) for the different solar activity periods and seasons

Beig, G.

Chakrabarty, D. K.

Pakhomov, S. V.

English

NASA Technical Reports Server

108
N90-28183
VARIATION OF D-RI_ION NITRIC-OXIDE DENSITY WITH SOLAR
ACTIVITY AND SEASON AT THE DIP _UATOR
D. K. (_nakrabarty 1, S. V. Pakhomov 2 and G. Beig 1
I Physical Research Laboratory, Ahredabad 380 009, India
2 Central Aerological Observatory, USSR State Caumittee for Hydromete-
orology & Control of Natural Environment, SU-123376, Moscow, USSR.
To study the solar control on electron-density(N ) in the equatorial
D-region, a program was initiated with Soviet collaboration in 1979. Total
31 rockets were launched during the high solar activity period, 1979-80 and
47 rockets during the low solar activity period, 1984-86 from 2]at_nba(8°N) to
measure the N profiles. Analysis of the data shows that the average values
of N for theehigh solar activity period are higher by a factor of about 2-3
co'red to the low solar activity values. It has been found that a single
nitric oxide density, [NO],profile cannot reproduce all the observed N profi-
les. An att_npt has been made to reproduce theoretically the observed N e pro-
files by introducing variation in [NO] for the different solar activity periods
and seasons.
INTRO_ION
To study the solar activity variation in electron density at the equato-
rial region an Indo-Soviet collaborative program was initiated in 1979. Under
this program total 47 rockets of type M-100 were launched during the low solar
activity period(1984-86) and 31 during high solar activity period(1979-80)
from Thurrba (8.5°N, 76.8OE), India tom easure the electron density of the D-re-
gion. All the observations were made for solar zenith angle (_) = 70-80 °.
To measure N a d.c. probe method was used for all the above flights. This
e . . .
avoided any varlablhty due to the different measuring techniques. The details
of the technique can be obtained from SINELNIKOV et al (1980). Using these
profiles, firstly the empirical models of N for low solar activity (LSA) and
high solar activity(HSA) periods have beenemade. An attempt has been made
to reproduce them theoretically. Analysis was also done for different months
and seasons. To reproduce all the observed profiles it has been found that
the nitric oxide density has to be varied both with solar activity and season.
ELZL-q'RON DENSITY M:)DELS
All the profiles obtained during LSA period(1984-86) and HSA period
(1979-80) have been averaged separately. Averaged profiles thus obtained for
LSA and HSA periods are plotted in Figure 1. These electron density data were
averaged in block of 5 km for the whole altitude range from 65-90 km. The
values of standard error in mean have been calculated. These are shown at
same altitudes(profile 1 and 2). For the sake of caT_=_rison, the Ne profiles
obtained by [v_LWrLY et a1(1972) from a mid latitude station for low and high
solar activity conditions (_= 60 ° ) are also shown (profiles 3 and 4). Profile
5 was obtained by Lan_aluir probe experiment carried out from Tht_rba, India
for LSA- period(SUBBARAYA et al., 1983). It is clear from Figuare 1 that the
averaged values of N for the HSA period are higher by a factor of about 2
e
ca'spared to the LSA values. The present HSA values are in agreement with the
values of Iv_--WI_Y et a1.(1972) below 75 km, but above this altitude the present
values are higher. The N values (LSA) of SUBBARAYA et a1(1983) agree well
with the present LSA valueebelow about 75 km.
Figure 2 show the electron density profiles obtained for the month of
https://ntrs.nasa.gov/search.jsp?R=19900018867 2020-03-19T21:13:28+00:00Z
109
April during LSAand HSAperiods. It is interesting to note here that like
in Figure l, N values in April do not showanysignificant variation. A plot
of N values _or a fixed height doesnot showany systenmticvariation. It
. , e
indzcates that the factors other that solar zenith angle also control the
electron density.
RESULTS AND DISCUSSIONS
A theoretical attempt has been made to reproduce the observed average
electron density profiles of Figure 1 by introducing the variation in nitric
oxide density for different solar activity periods and seasons. It has been
found that a single nitric oxide density profile can not reproduce the observed
No profiles of Figure 1. The nitric oxide density profiles which reproduce
the observed N e profiles are shown in Figure 3( profiles 1 and 2). In this
figure, two measurements of [NO] at Thurrba, one at HSA condition (TORKAR et
al, 1985) and other at LSA condition (TOtt_ATSU and IWAGAMI, 1976) are shown
(profile 3 and 4 respectively). The mid latitude profiles of BAKER et al
(1977) and MIRA (1971) are also shown in the same figure. It is clear from
this figure that the nitric oxide density values (profile 2) needed to repro-
duce the high solar activity profile of N are higher by a factor of about
5 cctnt_red to the low solar activity values (profile 1). It is also to be
noticed that, in general, the present [NO] values are higher compared to the
observed profiles obtained from the same location. The derived [NO] values
for LSA are greater than the measured values(profile 3) by a factor of about
ten. The present HSA values of [NO] are greater than the measured HSA values
of TORKAR et a1(1985) by a factor of about five. One can also see from this
figure that the present values are much higher compared to the mid latitude
values of profiles 5 and 6.
It appears from Figure 2 and 3 that besides solar activity variation
there could be a seasonal variation of [NO] also. To study these aspects,
N data were analyzed for different seasons(winter, smm_r, autunm, and spring)
fgr both LSA and HSA conditions. The nitric oxide density profiles required
to reproduce these electron density profiles have been derived. These are
shown in Figure 4 for LSA and HSA conditions. Lower scale represents the LSA
values of [NO] vahereas the upper scale represents the HSA values of nitric
oxide density. From Figure 4, the following interesting points emerge:-(l)
[NO] values show a seasonal variation during both LSA and HSA conditions. (2)
for LSA period, [NO] values are mininama in winter and maximtma in spring and
autt_rm seasons. The spring value of [NO] at 75 km are higher compared to win-
ter value by a factor of four. (3) For HSA period, trend of nitric oxide varia-
tion is almost in opposite phase c_red to LSA period below about 77 kin.
The [NO] value for winter season is higher by a factor of three at 75 km compa-
red to spring value of [NO]. Above 78 l_n, however, the spring values of [NO]
became slightly higher compared to winter and smmaer values. (4) Both surm_r
and winter values of [NO] show a minimum around 80 km for HSA period. Whereas
the autunm and spring values show a constant value of [NO] above about 75 kin.
It should be mentioned here that the auttman values are based on one month obse-
rvations only. (5) The LSA values of [NO] show a broad minimum ranging from
75 to 80 km for winter. It is also clear that the minimum in winter season
is at 75 lcn which shifts to 80 km for spring season.
CONCLUSION
Analysis of electron density data obtained by 78 rocket experiments car-
ried out at Thumba, India during the period 1979-86 have been done. In conclu-
sion following points are made:-
(1) The average value of N e for HSA is found to be higher by a factor
ii0
of 2-3 ccxrpared to the LSA values.
a particular month (April), the N
e
was found to be insignificant.
When data were analyzed for
variation with solar activity
(2) The above variation in N has been attributed to the variation in
nitric oxide density. _ theoretical analysis shows that the HSA
value of [NO] is higher by a factor of about five c_red to LSA
value.
(3) To reproduce the N values of different seasons, a seasonal varia-
tion in [NO] densit_ is needed.
REFERENCES
Baker, K. D., A. F. Nagy, R. O. Olsen, E. S. Oran, J. Randhawa, D. F. Strobel
and T. Tohmatsu, Measurement of the nitric oxide altitude distribution in
the mid latitude mesosphere, J. Geophys. Res., 82, 3281-3286, 1977.
Mechtly, E. A., C. F. Sechrist(Jr), and L. G. Smith, Electron loss coefficients
for the D-region of the ionosphere from rocket measurements during the ecli-
pses of March 1970 and November 1966, J. Atmos. Terr. Phys., 34, 641-646,
1972
Maira, L. G., Rocket measurements of upper atmospheric nitric oxide and their
consequences to the lov_r ionosphere, J. Geophys. Res., 76, 202-212, 1971.
Sinelnikov, V. M., G. P. Lvova, T. L. Gulyaeva, S. V. Pakhomov and A. P. Glotov,
A rocket radiobeacon experiment on the electron concentration profile measu-
rement in the bottom side of the ionosphere, Proc. satellite Beacon Syrrrp.,
Warszawa, Poland, 1980.
Subbaraya, B. H., S. Prakash, S. P. Gupta, Electron Densities in the equatorial
lov_r ionosphere from the Langmuir probe experiments conducted at Thurrba
during the year 1966-78, Indian Space Research Organisation, Sci. Rep. SR-
15-83, 1983.
Tobmatsu, T. and N. Iwagami, Measurement of nitric oxide abundance in equato-
rial upper atmosphere, 5. Geonm_. Geoelectr., 28, 343-358, 1976.
Torkar, K. M., D. Beran, M. Friedrich and S. Lal, Measurement of nitric oxide
and related parameters in the equatorial mesosphere and lower thermosphere,
Planet. Space. Sci., 33, 1169-1178, 1985.
111
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i. ImllSl141 w4ml - LISA (114&-N. X * lrl*-Mr)
), I_N'SINT w0all - HS_ (IITI-N, X • _-N* )
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I
ELECTRON DENSITY (C_ _1)
Fig.1. Empirical models of ave-
rage electron density for LSA
and HSA conditions obtained in
the present work alongwith the
profiles given by other workers.
a
IS
M
_P
I. LSA (lll4*llil
_. lISA (1170-111
,/
,y'/
//, L
14 _ il I il 4
EILIcCTRON DENSITY (CtI_ | )
Fig.2. Empirical averaged elec-
tron density profiles for the
month of April for LSA and HSA
conditions.
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70105
. i T
+ THUMIA II_I) IIIL*il. LSA.PAIIINt lq_
+ I,+MII IIP#I llyl-ll. HIA.PQIIINI WOIIK
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[NO] DENSITY (Cm 3)
Fig.3. The nitric oxide
density models obtained
in the present work for
LSA and HSA periods
alongwith the profiles
given by other workers.
I$
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Iii II Ii
I
LSA IHIII-III IIIII¢ IIIII_I" HSA (IIP|-III
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NUHOF_ DENSITY Ion( 31
Fig.4. The nitric oxide density mo-
dels derived for different seasons
and solar activity periods.
OR]GIP_AL PP,GE IS
OF ++OOR QUALITY


Variation of D-region nitric-oxide density with solar activity and season at the dip equator

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