Investigations on geomagnetism and aeronomy are carried out by IKFIA in Aeronomy Department consisting of 6 laboratories, and also at the Complex geophysical station in Zhidansk and Polar geophysical observatory in Tixie Bay. The experimental base of the Aeronomy Department is the Yakutsk meridional station chain from Yakutsk to Kotel’ny Island equipped by the installation complex in order to observe geophysical phenomena with the flux-gate and induction magnetometers, TV all sky cameras and multi-channel photometers, vertical and oblique sounding ionospheric stations, riometers and also multi-channel VLF-noise registers, thunderstorm-pelengator-range finder, Fabri-Perot interferometers and spectrometers.

The Institute participates in the international projects: “Global geomagnetic observations along the 210° magnetic meridian”, INTERMAGNET, CRISTA-MAHRSI, PSMOS, INTERBALL.

One-minute digital geomagnetic observation data obtained on the territory of Yakutia are accessible for common use through INTERNET, the magnetic data from Tixie are transferred in the quasireal regime into the World Data Center (Japan) to determine the operative auroral indices.

The main scientific direction of the Aeronomy Department is the study of physical processes in the magnetosphere, ionosphere, and thermosphere during magnetospheric disturbances under different condition in the solar wind and interplanetary magnetic field. It is studied types and structures of the auroral disturbances during magnetic storm and substorm, regularities of the formation of the main ionospheric through and SAR-arcs, the origin of VLF-noises and the thunderstorm activity,the thermal and wind regimes of the high-latitude thermosphere.

Main Scientific results for 1995-1998ãã.

The vast experimental data on the temperature measurements in different layers of the upper atmosphere with the Fabri-Perot interferometer and spectrograph SP-48 have been accumulated in the Institute. The particularities of the temperature regime and large-scale dynamics of the subauroral and auroral thermosphere and mesosphere under quiet and disturbed geomagnetic conditions and also in the solar activity cycle are studied. Results testifying about realized by means of the upward propagation of wave disturbances of a type of planetary waves have been obtained. It has been revealed the azimuthal nonhomogeneity in parameters of the internal gravitation wave horizontal components which can be a sequence of filtration by the background wind.

The joint study of synchronous magnetic and optical observation data at the 190-210° magnetic meridian station chain are carried out. It is established that there is a relationship of the generation of high-latitude Pi2 pulsation to the formation processes of the luminosity waves of the aurora arcs; Pi3 pulsation to the generation and southward propagation of luminosity structures stretched along the meridian (N-S aurora); excitation of geomagnetic pulsation Pc4-5 and the amplitude modulation of pulsation Pc1-2 and IPDP to the large-scale luminosity structure formation during the geomagnetic disturbances. These results are used to make more precise the structure and dynamics of the internal magnetosphere. The possible scenario of the Pi2, Pi3, Pc4-5 pulsation excitation and also the equivalent current system responsible for Pi3 and Pc4-5 pulsation excitation have been suggested.

Characteristic peculiarities in latitude distribution of the density and temperature of ionospheric plasma being the signatures of the day-side cusp region have been found by using the satellite and ground-based measurements of high-latitude ionospheric data at the Tixie station is developed. The asymmetry of the electron density and temperature in the minimum of the main ionospheric trough in the northern and southern hemispheres has been revealed.

The SAR-arcs dynamics by the spectrophotometric observation data in Yakutsk with an advent of ionospheric and satellite data is studied. It was shown that the SAR-arc is evolved in the ionosphere F-layer where the local minimum of electron density is formed and reflections on ionograms typical for the polarization jet, or SAID structure, appear. The obtained results are used in order to make more precise the internal magnetosphere structure during quiet and disturbed periods.

The principal possibility for detection of the expected substorm center location tens minutes before the break-up beginning is shown by using the measurements of the background luminosity intensity at the Yakutsk and Noril’sk meridional chains.

Two geomagnetic storm classes and four types of high-intensity long-duration continuous auroral activity (HILDCAA) are studied. The relations between HILDCAA’s types, geomagnetic storm classes and different solar wind structures has been determined. The essential role of the IMF turbulence level on geoeffects has been shown.

The close anticorrelation (r » - 0,83) of the thunderstorm activity in the east of Siberia with the solar activity has been found by observation results of regular electromagnetic VLF-noises for 1979-1994 in Yakutsk. From the analyses of the solar eclipse effects it is obtained that the diurnal variation of regular VLF-noise intensity at frequencies lower 10 kHz registered in Yakutsk is approximately by half determined by the world thunderstorm activity and by half by propagation condition.

The influence of the solar wind density and the IMF module on geomagnetic activity variations (Aa index) in solar cycle has been revealed. The distribution of the parameters is shown to manifest itself in the form of a trend and long-term variation of Aa.

Auroral absorption variations dependent and independent on the IMF sector structure have been found by using riometric observations in Tixie for many years. The first ones are caused by the superposition of the solar wind electric field and the electric field owing to the quasiviscouse friction, and the second ones are due to the change of mutual location of planes of the magnetosphere tail plasma sheet and the geomagnetic equator.