L. Bankov

An instrument for total ion drift velocity measurements aboard the ‘Intercosmos-Bulgaria-1300’ satellite

Abstract The ‘INTERCOSMOS-BULGARIA-1300’ satellite was launched on Aug. 7/81, to investigate ionospheric plasma dynamics. It had a perigee of 825 km, an apogee of 906 km and orbit inclination of 81.2°. The satellite was three axis stabilized within ±1° on each axis. The ion driftmeter, ID-1, aboard this satellite was intended to measure ion density irregularities, the ion drift velocity and photoelectron fluxes. The purpose of this paper is to present a brief description of the ID-1 instrumentation and to show the first results obtained from the flight instrument.

Critical Ionization Velocity (CIV) experiment XANI onboard the INTERCOSMOS 24 — “ACTIVE” satellite

Abstract Satellite INTERCOSMOS-24 “ACTIVE” was launched on September 30 1989, with an initial apogee 2500 km, perigee 530 km and an orbital inclination of 82.2°. Under “ACTIVE” project, a wide number of plasma diagnostics instruments were especially designed to study the ionospheric response to high power VLF transmitter emissions, by means of satellite-subsatellite system during this mission. As a separate part of this project, a Critical Ionization Velocity (CIV) experiment called XANI (Xenon ANomalous Ionization) had been carried out to study neutral gas/plasma interaction processes in the ionosphere using neutral Xe gas injection. Seven Xe gas release experiments had been realized at daytime high latitude ionosphere. In this paper an Ion Drift Meter (IDM) and Retarding Potential Analyzer (RPA) data concerning transverse ion drift velocity vector measurements and total ion density variations during gas release experiment are shown. Two examples of the RPA data, taken after the beginning of Xe injection, show some prompt ionization at the ionization front about 30% in comparison with the background ion concentration. Horizontal ion drift of few hundred meters per second, transversal to the satellite velocity vector, had been observed at the ionization front.

Energy deposition in the polar ionosphere as determined by measurements aboard ‘INTERCOSMOS-BULGARIA-1300’ satellite

Abstract Data were obtained from the measurements of optical emissions, ion drift, DC magnetic field and energetic particles, on board INTERCOSMOS - BULGARIA - 1300 satellite. In two cases of night-time passes through auroral oval, an estimate has been made of the energy input by particle precipitation and Joule heating. In order to determine the Joule heating, the Pedersen currents flowing in the lower ionosphere were determined. In orbits 231 and 203 Pedersen currents of 0.94 Am −1 and 0.71 am −1 were observed. From these values estimates of Joule heating rates of2 × 10 −7 Wm −3 and8 × 10 −7 Wm −3 were obtained. The integral energy deposited by the precipitated particles was also estimated in the current systems regions. The possibility for identification of the auroral electrojet based only on satellite data is pointed out.

A case study of subauroral ion drift velocity jets by means of dynamics explorer-2 and intercosmos bulgaria-1300 satellites data

Abstract Satellites INTERCOSMOS “Bulgaria-1300” (ICB-1300) and Dynamics Explorer-2 (DE-2) were launched close together early in August 1981. The satellite data base from both DE-2 and ICB-1300 covers almost a two years period. Data from both satellites were used to examine the longitudinal behavior of a few selected simultaneous subauroral ion drift (SAID) events in the late evening and earlier morning hours of magnetic local time (MLT). SAID velocity jets occur as a narrow region at the equatorward edge of the auroral oval in the westward direction in the evening hours, simultaneously in both hemispheres. It is shown, that the polward component of the DC electric field measured from ICB-1300 corresponds well to the ion drift velocity jets observed in the Ion Drift Meter (IDM) on DE-2 with some longitudinal extent of more than three hours MLT in the evening sector. In a specific case (orbit 705 of ICB-1300), we observe downward current associated with a SAID event of about 1.8 μA/m 2 , corresponding to the previously reported current measurements on DE-2 (orbit 796) of about 2.1 μA/m 2 . The simultaneous SAID observation taken in the earlier morning hours of the ion drift velocity distribution, shows an existence of velocity jets up to 0130 MLT.

VLF plasma waves observed during the xenon gas releases on the ACTIVE satellite

Abstract During the ACTIVE satellite mission in 1989/90, neutral xenon gas was released from the satellite. The release, 50g/sec, with velocity 250m/sec quasiperpendicular to the geomagnetic field occurred at different ionospheric altitudes. Parallel with the release process the VLF plasma waves (20Hz–20kHz) were recorded. The very high level of VLF emission during the release was registered and observed for some frequencies to extend some seconds beyond the release. It suggests for creation of expanding plasma cloud close to the satellite. It is difficult to use these observation for a clear CIV test because of incomplete darkness experimental conditions. This paper presents the observed VLF emission characteristics.

Seasonal dependence of the ion density irregularities at the magnetic equator from OGO-6 retarding potential analyzer data

Abstract The morphology of the nighttime F-region irregularities is a subject of several satellite in-situ and ground-based optical and radar measurements. In this paper, we use the RMS variations of the total ion current as measured by retarding potential analyzer (RPA) aboard the OGO-6 satellite. More than 600 orbits were used for a statistical examination of the occurrence frequency of the irregularities at night (between 19 and 06 h LT) over the magnetic equator for spring and summer conditions in 1970. We discuss a possible statistical relationship between these OGO-6 irregularity data and thunderstorm activity data from OSO-5 for the same period.