Terrestrial myriametric radiation from the earth's plasmapause

Terrestrial myriametric radiation (non-thermal continuum) observed by the GEOS 1 spacecraft is used to determine the radial profile of plasma density at the equatorial plasmapause. The method utilises the properties of a radio window through which the radiation propagates. The radial density profile obtained by remote sensing is compared with that implied from natural electrostatic emissions as the spacecraft approaches the equatorial source region. The TMR profile appears to be that of the cold plasma whereas the frequencies of the intense non-equatorial emissions beyond the plasmapause are governed by the hot and cold components. Ray-tracing and polarisation computations indicate that a simplistic interpretation of direction-finding measurements using the spinning dipole technique could lead to erroneous source directions under certain circumstances. In such cases if the spacecraft orientation is known corrections can be applied to yield the true direction.