Plasma conditions in the polar ionosphere observed in SPW experiments of PPS system on board the Ohzora (EXOS-C) satellite.

Abstract

The data of the stimulated plasma wave experiments (SPW) obtained from the planetary plasma sounder (PPS) aboard the Ohzora (EXOS-C) satellite have been analyzed for the initial three months. From the ionograms of SPW experiments 1) vertical profiles of the topside ionosphere, 2) irregularity of the plasma distribution and 3) identification of the modes of the naturally emitted plasma waves have been obtained. The studies on these subjects lead to the following results.(i) In the polar region ionosphere, the auroral particle precipitations generate the intense plasma waves even in the satellite level.(ii) Associated with the generations of the intense plasma waves caused by the particle precipitation, there are irregularities of the plasma distribution in the topside ionosphere which become the origin of the scattering effects on the transmitted RF pulses.(iii) Enhancement of the electron density takes place caused by the enhanced precipitation of the aurora! particles in the auroral region. At the same time remarkable heat input which is indicated by increasing of the electron temperature is also confirmed.(iv) Near the auroral zone in the lower latitude side than the aurora! regions, there is also the region where the heat input is taking place in milder manner than the case of the auroral regions.(v) Large energy input into the auroral zone triggers a relatively large scale disturbance propagating in the polar cap ionosphere in the form of the traveling ionospheric disturbance (TID).

Observation of electron density by the impedance probe on board the Ohzora (EXOS-C) satellite.

“…The increase of the plasma temperature suggests the heating of the plasma just inside the plasmapause. The result is consistent with the results of the sounder experiment (OBARA and OYA, 1985). The heating of both occations may be similar to the excitation process of SAR arcs in high geomagnetic activities.…”

Plasma Waves and Sounder (PWS) experiment onboard the Planet-B Mars orbiter

“…5, it becomes clear that the signal can be detected by the sounder receiver with medium gain. As has been calculated by Franklin and Maclean (1969), and discussed by Obara and Oya (1985), the mismatch loss due to a variation of an antenna impedance in space is unavoidable. When the frequency changes to 300 kHz, which is a very possible frequency range for sounding the Martian ionopause, the antenna impedance in the vacuum takes a resistance of 0.6 Ω and reactance of -7.5 kΩ for example.…”

“…The first observation across the plasmapause was made by the Jikiken (EXOS-B) satellite (Oya et al, 1981;Oya and Ono, 1987). The first digital system of the plasma sounder was developed in the topside sounder experiment of the Ohzora (EXOS-C) satellite Obara and Oya, 1985).…”

Lunar Radar Sounder (LRS) experiment on-board the SELENE spacecraft

“…Then, it is also needed to realize a digitalized method for the data analysis and recording. We can improve the instrumentation by adopting new technology developed by the plasma sounder experiments which have been established through the plasma sounding of earth's magnetosphere, plasmasphere and ionosphere by using satel-lites EXOS-B (Jikiken) Ono, 1981, 1987), EXOS-C (Ohzora) Obara and Oya, 1985) and EXOS-D (Akebono) (Oya et al, 1990). The concept of the plasma sounder is originated in the topside sounder satellites of Alouette and ISIS (Franklin and MacLean, 1969;Jackson and Warren, 1969), namely the plasma sounder has capability of transmission of high power RF pulses into plasma through long deployed antennas.…”