First remote sensing of the plasmapause by terrestrial myriametric radiation
The Earth's plasmapause is a source of natural radio emission in the myriametric wavelength range (λvac∼10 km) and several mechanisms have been proposed for its generation. One such theory advocates the mode conversion of electrostatic waves to electromagnetic radiation by propagation through a radio window. The window properties are such that the escaping terrestrial myriametric radiation is beamed away from the magnetic equatorial plane at an angle which depends on the plasma parameters at the window. This property should allow myriametric radiation observed by spacecraft to be utilized for remote sensing of the plasmapause. An example derived from the satellite GEOS 1 is presented here in which a radial profile of cold plasma density is obtained for the first time by this technique. The method may also allow a better identification of those electrostatic modes existing in the mixture of hot and cold plasma components at the plasmapause and beyond.