Remote sensing of planetary plasma by means of natural radio emissions

Voyagers 1 and 2 discovered radio emissions at Jupiter, Saturn and Uranus which were similar to those already studied in the Earth's magnetosphere. Terrestrial myriametric radiation, TMR, emanates from electrostatic upper hybrid, ESUH, waves, the conversion being believed to occur as described by the linear mode conversion window, LMCW, theory. A technique, based on the theory, has been devised which allows TMR, observed by satellites, to be used to remote-sense the source regions so as to obtain the location and plasma density of the source plasma. The technique can also be applied to study the sources of the analogous radiations observed at the other planets: Jovian kilometric radiation and narrowband electromagnetic emissions at Saturn and Uranus. The results of using this technique with the four planetary radiations are presented. They provide further evidence for the validity of the LMCW theory and for the importance of plasma density gradients in the conversion process.