Radio sounding of the plasmapause by a geostationary satellite

Low frequency radio sounding by a geostationary satellite has been planned to observe time variation of the plasmapause and effects of the plasma convection. The plasmapause is an abrupt outer boundary of the plasmasphere located at geocentric distance of about 4 earth radii in the equatorial plane, and the plasma density drops from 102 - 103/cm3 to 1 - 10/cm3 in a plasmapause width of about 600 km. LF-VLF radio waves transmitted inward from a geostationary satellite (6.6 earth radii) will be reflected outward by the plasmapause. Thus, a plasmapause sounder is designed to transmit 13-bit Barker coded pulses (baud length of 0.5 msec) of 70 watts peak power at frequencies of 10 kHz - 2 MHz in a pulse interval of 0.5 sec from a 400-meter cylindrical dipole. But, a peak power of 700 watts or more will be required when strong non-thermal continuum emissions occur below 200 kHz on the morning side during a geomagnetically disturbed period. This will open new area of radio sounding in the magnetosphere. (auth.)