PROBLEMS OF GEOCOSMOS

Proceedings of the 7th International Conference "Problems of Geocosmos" (St. Petersburg, Russia, 26-30 May 2008)
ANALYSIS OF CLUSTER AND IRIS RIOMETER DATA OBTAINED
DURING EXPERIMENTS ON IONOSPHERIC MODIFICATION CARRIED
OUT 16 FEBRUARY 2003
A.L. Maulini 1 , A.L.Kotikov 1 , A.Gavrasov 2 , V.I. Odintsov 3
1 Institute of Physics, St.Petersburg University, St.Petersburg, 198504, Russia, e-mail:
maulini@geo.phys.spbu.ru; 2 Kostroma State University, Kostroma,Russia; 3 Institute of Terrestrial
Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN), Moscow, Russia
Abstract. This article is dedicated to one of the actively developing line of investigation in space
plasma physics such as artificial modification of the ionosphere. Experiments carried out using
Tromso heating facility with pump wave frequency of transmitter 4.04 MHz with square
modulation period 10 minutes in 16 February 2003 is considered. This event was selected because
of orbits projections of CLUSTER satellites along magnetic field lines went nearby disturbed
region in ionosphere according to Tsyganeko model (T96). Electric, magnetic field and electron
density data from CLUSTER satellites and IRIS imaging riometer data using wavelet, short time
Fourier transform and spectral time analysis developed in IZMIRAN are analyzed. It is shown that
effect is clearly observed in IRIS imaging riometer data (16 February 2003) right in the beam
where the heating spot is. Also effect of heating is observed in CLUSTER data when satellites
cross magnetic field lines conjugated with disturbed region. Thus it is experimentally shown that
functioning of heating facility affects not only ionosphere but also the coupled ionosphericmagnetospheric
interaction system.
Introduction
Aim of the experiment maid on 16 February 2003 by EISCAT heating facility in Tromso was the study of
magnetospheric disturbances originated from modified ionosphere. The pump wave of 4.04 MHz had been
used for ionospheric conductivity modification from 19:55:00 to 23:59:59 UT. The heating wave in
eXtraordinary polarization (X-mode) and square modulation regime with 5 minutes ON and 5 minutes OFF
cycle was employed.
Generation of the disturbances made by enhancement of ionospheric conductivity in presence of the
background electric field was considered theoretically by Maltsev et al. (1974), Stubbe and Kopka, (1977),
Oguti and Hayashi (1984). Maltsev et al. (1974) have found analytical solution for some kinds of
conductivity inhomogeneities, for more general cases numerical modeling should be used. The process can
be described shortly as follows: in the region with enhanced conductivity electrical field can be considered as
homogenous, at the border of the region appear field aligned currents, out of the disturbed region electric
field diminishes as two-dimensional dipole. Disturbances of the electric field and related field-aligned
currents propagate into magnetosphere with Alfven speed. This propagation is supposed to provide
disturbances in coupled magnetospheric-ionospheric system much stronger than initial ones. And this work
tries to check this supposition using different kind of experimental data.
Satellite observations and analysis
We used data from Cluster – satellites of European Space Agency. This is a group of four satellites
forming a tetrahedron what make possible to measure different parameters of cosmic plasma not only from
one point in space but from a volume. Orbits of satellites were calculated down to the ionosphere ( about 100
km above the Earth surface) along magnetic field lines using Tsyganenko model (T96) with follows
parameters: DST = -27, By = 2.9 nT, Bz = 2.3 nT, pressure
of solar wind Psw = 2.5 nPa. According to calculation the
disturbed spot at high of ionosphere has about 25 km in
diameter.
.
along magnetic field lines.
Fig.1 Results of calculation of disturbed magnetic tube
and projection of clusters’ orbits down to the Earth surface
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