An approximation of the height of the O+ - H+ transition level for use in IRI

A set of data including over 1400 transition level (TL) encounters of the OGO-6 satellite is used to construct analytical presentations of this altitude upon dip-latitude and longitude. The formula represents the TL variation between ± 50° dip-latitude and 20 h and 04 h local time interval. The data were obtained in the high solar activity period in 1969 and 1970.     

An instrument for DC electric field and AC electric and magnetic field measurements aboard ‘Intercosmos-Bulgaria-1300’ satellite

The instrument IESP-IPMP represents the complex unit measuring the vector of the DC electric field, the vectors of the electric and magnetic field in the frequency range of 0.2 – 6.5 Hz (wave form), autocorrelation functions of waves with frequencies of 0.1 – 5 kHz, and wave amplitudes in 8 bandpass channels. Some results are shown and compared in the various frequency ranges.     

The improvement of IRI profiles of O2+, NO+ and O+ by means of airglow measurements

Methods were suggested in /1,2,3/ to find the maximum electron density N_mF (or N_mF2) and the) corresponding height h_mF (h_mF2) in the ionosphere through a combination of measurements on two airglow lines: the UV oxygen line at λ135.6 nm and the red oxygen line near λ630 nm.     

Latitudinal asymmetry in electron and ion density distribution in southern and northern hemispheres

With data of satellite INTERCOSMOS-BULGARIA-1300 northern and corresponding southern hemisphere plasma densities have been compared. Southern densities are greater in the ?90 to ?180 and +30 to +120° ranges. The opposite is true for ?60 to +30°. No asymmetry has been observed during daytime. These results are explained by the variations of the magnetic declination.     

Thermospheric heating at high latitudes as observed from intercosmos-Bulgaria-1300 and dynamics explorer-B

This paper reports the results of the first direct comparison of near simultaneous measurements obtained by the INTERCOSMOS-BULGARIA-1300 and the DYNAMICS EXPLORER-B satellites. The ICB-1300 is in a near circular orbit at a mean height of about 850 km. The DE-B satellite in an elliptical orbit is sometimes directly below the ICB-1300 satellite providing an opportunity to investigate the response of the thermosphere to particle fluxes from the magnetosphere. Energy fluxes in the range 0.2–15 keV are obtained from an energetic particle analyzer on board the ICB-1300 satellite. The thermospheric composition and density are obtained by a neutral gas mass spectrometer (NACS) on the DE-B satellite. During the period 20 August–20 November, 1981, observations show tht the times and locations of maxima in magnetospheric energy deposition coincide with regions of maximum thermospheric upwelling characterized by composition changes.     

Effects of small-scale plasma disturbance on the IKB-1300 spacecraft potential

The potential of the Intercosmos-Bulgaria-1300 (IKB-1300) satellite launched to a circular orbit at an altitude ～900 km was measured with several instruments. Care was taken to equalize the potential along the satellite surface. The satellite was placed inside the conducting screen and the solar cells had a metal coating. The satellite potential slightly varied along the trajectory and in the typical case it was “?2”B that corresponds to 5 kTe/e. While the satellite crossed the auroral zone small-scale fluctuations of plasma and field parameters, known as shocks, were recorded. In this region a sharp decrease of the satellite negative potential is often observed. In this case the potential variations well correlate with the increasing flux of energetic electrons. The observed variations can be explained by secondary electron emission from the satellite surface.     

Bottomside N(h) profiles over Vietnam and their comparison with IRI

Over 70 ionograms were selected from the ground-based ionosonde in Hanoi, Vietnam at times when the AE-E satellite passed above the station. N(h) profiles were calculated from ionograms and thus compared with the IRI model and local AE-E ion densities. For the purpose of the presentation, 15 profiles were selected to cover all seasons and local times. The comparison shows that the observed daytime N(h) profiles have significantly higher gradients below the F2 peak density while at night the observed and the IRI profiles almost coincide. The difference is more pronounced in summer than in equinox. Wintertime comparisons are quite limited and do not lead to reliable conclusions. N_mF2 values taken from the CCIR programme are compared with those observed. The comparison shows that the deviations are not so large.