The correlation between lower ionosphere disturbances, geomagnetic variations and radiowave absorption is an important geophysical problem. The correlation is investigated between the electron density profile structure and riometer absorption, and between the absorption and the H-component magnetic field, in order to determine the relation between the (e)-profile parameters and the geomagnetic field variations

Arkhipov, J. V.

Laikova, V. F.

Soldatov, V. A.

Zelenkova, L. V.

English

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236
ON THE RELATION BETWEEN THE ELECTRON CONTENT OF THE IONOSPHERIC
D-REGION_ VARIATIONS OF THE RIOMETER ABSDRPTIDN_
AND THE H-COMPONENT OF THE GEOMAGNETIC FIELD
L.V.Zelenkova_ V.A.Soldatov, J.V.Arkhipov, V.F.Laikova
Research Institute of Physics, Leningrad State University_
Stary PetergoF, 1989_4_ Leningrad, USSR.
The correlation between lower ionosphere disturbances, geomagnetic
variations and radiowave absorption is one of the most actual problems of
geophysics.
In this work we investigate the correlation between the electron density
profile structure and riometer absorption, and between the absorption and the
H-component magnetic field, in order to determine the relation between the
[el-profile parameters and the geomagnetic field variations.
I. To calculate theoretically the electron density behaviour during
disturbed conditions from riomet_r/absorption data, one can use the well-known
formula: [el=_'q_"_ where q (cm _ ) is the ion production rate and _ (c_e)
is the effective loss rate.
PARTHASARATHY [1966] presents the relations between riometer absorption and
the integra_ precipitating electron flu:_ with E>40keV in the following form:
A(dB)=3.3 I_- V3(>40keV)'.
ZELENKOVA [1988] showed that provided the integral precipitating electron
flux has the power form as J(>E)=k.E "r we can find the flux parameters _ and
. For _ =2: k=3,3 "a I_¢40JA a, Thus_ for each value of riometer a_scrption, it
is possible to obtain the differential preripitating electron flux responsible
(or _t.
Then we obtain the ion production rate using the formula from paper by
KHVOROSTOVSKIY [I?B7].
2. To determine the height profile of [el, the investigations of effective
loss rate variations were made using the published data referenced in the paper
by GLEDHILL [1986]. All the height profiles were separated into 4 groups:
I) _4 height profiles for the day-time quiet conditions (12 profiles),
2) _Z height profiles for the night-time quiet conditions (7 profilesl,
3) _$ height profiles for the day-time disturbed conditions (13 profiles),
4) _Ism height profiles for the night-time disturbed conditions (5 profiles).
Mean profiles for 4 types of conditions are shown in Fig.1. The value of the
disturbed (both day-time and night-time) effective loss rate is less than the
quiet one as seen from Fig.! even taking into account the considerable error
(shown). The fact of dependence of the effective loss rate on ionospheric
disturbance level was established in the paper by ZELENKOVA [1981]. Using a
3-ion D-region model for the height range of _ =[M']/[e]>1, the analythical
deoendence was derived also in that paper.
Because the formula from paper by ZELENKOVA [1981] is correct when _ >I, we
used also a combined profile of _ , where effective loss rate was calculated
for the heights from 5_km to the height where _IJ becomes equal to 2 I_ 7 csas_,
and such a value of _ was a_sumed up to h=95km. In the height range 95-120km
varied uniformly from 2"10 "_ to 2"I_ _ cm_s "¢ [ADAMST1965].
3. The experimental rocket profiles of the electron density were taken from
the work of MIYAZAKI [197B] in form of a catalogue [NESTEROVA,I?B5]. To compare
the calculated and the experimental profiles, we chose the parameter
_O0 =([e]¢ [el )/[e]_ (I)
where [e_ is the calculated electron concentration and [e]_ is that measured
during the rocket ascent.
Moreover, the availability of both ascent and descent rocket electron
https://ntrs.nasa.gov/search.jsp?R=19900018892 2020-03-19T21:13:00+00:00Z
237
dmnsitv orofi!e data allowed us to estimate a similar parameter:
_ =(Eel a . [e]d)/r_e.a_ (2i
where [e]_ is the electron density corresponding to the fixed height during the
rocket ascmnt, _m] d _eing that obtained during the_rocket descent.
Tab.l shows the absolute values of parameters l_J.l| and I_;I.
The estimation of _00 was performed with _4 (mean nioht-time disturbed
conditions profileT abbreviated as NGN in Tab.l) using combined _ profile
(abbreviated as NGT in Tab.l) for the riometer absorption between _._ and 5dB.
4. Experimental profiles of [e] from the paper by MIYASAKI [1978],
complemented with those from PFISTFR [1967] and DERBLOM [1973l were analysed by
ZELENFOVA [1982] by using four parameters which characterise the [el-profile
structure of the disturbed D-region. These are h# - height of 10a cm "J electror
appearance, h_ - height o_ strong enhancement of [e]-gradient and N_ -
concentration of the "step" bottom, Na- cnncentration of electrons at h=_5_m.
Tab.2 shows the variation of the above mentioned parameters versus riometer
absorption between 0.3 and 5 dB.
5. Generally accepted parameter that reflects magnetic field variation
during geomagnetic disturbances is the AE-index.
We attempt to connect the electron density pro_i!e parameters with the
AE-index.
_rofiles were compiled from the catalogue of MCNAMARA [!978] and also from
the catalogue of NESTEROVA [1985]_ where they are given iea digital form. Only
the auroral zone profiles during disturbances were selected, which corresponds
to the inoexes o-'_,._, [NESTEROVA,IQB5;. . MCNAMARA,197B].
Thus, 44 profiles for night-time conditions were _hosen.
All the profiles were selected into different groups according to the
AE-index value in the _ollowing manner: 0 <AE <100(6), 100 <AE ,_208(9),
20_ _AE _;3_0(8), 300 _AE _400(_). 40_ _AE <500(7), 50_ _AE {600(2). AE_ 600(4).
Attention was paid to geographic location of stations: Andoya(69.1_N,
I_ E)(25), Syowa(69.5_S,39_E)(111, College(64.9 N,212_E), Churchill(58. N,
265.8mE)(2) (the number of profiles is in the brackets).
Parammters that characterise the electron density distribution in the
D-region are the heights of appearance of the electron density equal to l_acm "a,
10ac_ m, 10#cm °m, respectively.
Mean profile o_ the electron density distribution was calculated (Tab.31.
6. To _ompare the electron density variations obtained using AE-index with
:-parameter model _see part 4), we study the relations between the riometer
absorption and AE-index. Wm got the ionospheric data from Pinnish Academy of
sciences and compared them with AE-index. We explore the data from 1978-t979
years. Two intervals were chosen: 19-2_LT and 23-01_LT. Such dependences are
shown in Fig.2 for the stations Kevo and Sodankyla. One can conclude from the
Fig.2:
l)the absorption for the night-time (23-01_LT} is greater for farther to the
south station (for the same AE-index);
2_both for Keys and Sodankyla the riometer absorption is greater at 23-01 _ LT
than !9-22_LT.
Using Fig.2, it is easy to obtain the riometer absorption for each value o_
AE-index.
Tab.3 summarises the results from Fig.2 and from the catalogue. The
designations are: AE is the AE-index in_, N is the number of profiles, A,dB is
the magnitu0e of the r_ometer absorption; h(N;@_), h(N_&)_ h(N_$)_ are
the heights of appearance of the appropriate electron density.
Conclusions from the data of Tab.l, __ and 3. :
I. Theoretical investigations allow us to determine the height distribution
of [el with relative error less than 100%. At the same time, the experimental
measurements are subject to relative error I_scent and descent) as lapse as
50%. That reflects a wide variability of auroral ionosphere, rather then
imprecision of the e:<perime_t. _!_!_,_._. _
OF POOR QUALIT_
238
2. Both experimental and theoretical investigat_on_ shows the enhancement of
riometer absorption due to:
,_) the appearance of equilibrium electron density about 102cm "J mt heights
h<50km (lower part of D region),
b) the increase of [el by more than an order of magnitude in the L,pper part
of the D-region (h>gOkm).
Parmmeter hf characterize thm hardness of electron flux spectrum, while the
paramet_-s N 2 and N3 characterize the intensity of the flux.
As seen from Tmb.2_ the best accordance between the experimental and
cslc_l!mted (restored_ parameters of [eS-profile appears. The discrepancy
between the hsm and h 4 (!9-22), h_ (23-BI) is exo]ained by the fact that the
station becomes sltuated northward o4 the precipitation zone during the large
values of AE-index.
REFERENCES
Adams G.W., Masley A.J. Production rates and electron densities in the !ower
_onosphere due to Solar cosmic rays. O.Atm. Terr.Phvs._27,289,1965.
Derblom IJ._ Ladel] L. D-region parameters at high latitudes obtained from
rocket experiments. _.Atm. Terr. Phys.,35,212_1973.
Gledhill O.A. The effective recombination coefflcient of electrons in the
ionosphere between 5_ and 150 km. Radio Sc_.21_399,1986.
Khvorostovskiv S.N., Zelenkova L.V. Geomagn.and aeron._27,599,1gB7{in Russian).
McNamara L.F. Ionospheric D-region profile data base. Report UAG-67_IqT8.
Mechtly E.A._ ]owhill S.A., Smith L.G. Changes of lower ionosphere electron
concentrations with solar activity. J.Atmosph. Terr. Phys.34,1899,1_72.
Miyazakl S. Innospheric plasma probe studies and ionospheric structure studied
by space vehicle observatlons. O.Radio Res. Lab.25,153,1978.
Nesterova !.I._ _insburg E.I. Catalog of D-region electron density profiles n_
the ionosphere. Novosibirsk_1985(in Russian).
Varthasarathy R., Berkey F.T., Venkatesan D. Auroral zone electron flux and
its relation to broadbeam radiowave absorption. Planet. Soace Sci.14,65,1966.
Pfister W. Auroral investigations by means of rockets. Spa_e Sci.Rev.
7,642_1967.
Zelenkova L.V. Dissertation,1981(in Russian).
Zelei_kova L.V. D-region _lectron density distribution. Geomagn. Res.
N 14,181,Ig76.
Zelenkova L.V. Structure o_ the electron density profile during auroral
disturbances. Magnetosph.res. N 1,187_1982(in Russianl.
Ze!enkova L.V., Soldatov V.A. Restoration of the impinging electron
differentia] fluxe_ from riometric absorption. Magnetosph.res. N II,133_1988
(_n Russian).
ORIG_NP,L PP,GE IS
OF POOR QUALITY
TAI4LE i
70
75
80
85
90
95
100
0 47
0 47
0 44
0 68
0 53
0 85
1 12
O. 62 0.59
O. 70 0.45
0.34 0.5(I
0.76 O. 60
O. 75 0.47
0.98 0.36
O. 99 0.4(I
TABLE 2
._ -| -J
A, dB hlm,km h¢c,km h z ,km N z ,cm Njm, cm Nje, cm
239
0.3 68 65 78 3 10 3 1(I 4 I0
0.5 60 56 80 i0 7 IC) 6 i0
1.2 58 55 83 2.5 I0 8 10 i0
1.3 57 - 82 2 i0 10
1.5 58 55 83 10 3 I0 2 10
2.6 55 52 75 8 I0 4 I0 3 I0
- 5 i0 6 I05.0 55 5[) -
TABLE 3
4 AE, r < N A, dB A, dB hlo I, km hto j, km hlo _, km
(19-22) (23-01)
O - i00 6 O. 2 O. 4 64_+9 74+4 83-+4
I00 - 200 9 0.5 0.7 62+2.2 72_+5 82_+5
200 - 300 8 0.9 1.2 50+8 67+6 80_+2
3[)0 - 4[)0 8 1.3 1.7 63±5.5 73+3.5 80-+3
4(10 - 500 7 1.5 2.5 79+8 79_+8 87+8
500 - 600 2 2 . 0 3, O 83+3 89&i 96+4
> 600 4 2.3 4.0 67--+5 65__5 75+5
tx
,_ i_
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0'o_- \\ _ ",
-8 -6 -_ -2
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ORIGINAL PAGE IS
OF POOR QUALITY
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On the relation between the electron content of the ionospheric D-region, variations of the riometer absorption, and the H-component of the geomagnetic field

On the relation between the electron content of the ionospheric D-region, variations of the riometer absorption, and the H-component of the geomagnetic field

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