The use of geomagnetic pulsations in determining magnetospheric plasma properties

Abstract

The existence of cold or cool heavy ions in the magnetospheric plasma of the earth has been known since early GEOS-I ion composition experiment results in 1977 (Geiss et al. 1978). Helium (He+) and oxygen (O+) relative concentrations of up to 50% of the total ion concentration were found. The reliability of these particle concentrations are difficult to estimate. Unresolved wave modulations, giving rise to plasma flows and other problems including spacecraft charging. make concentration measurements difficult. Mauk (1984) has recently shown, by computer simulation, that particle concentrations measured in association with linear interaction between a wave and He+ ions may be artificially inflated by an order of magnitude. An extremely simple and sensitive measure of heavy ion (He+, O+) relative ion concentrations can be made using the bounding surfaces associated with the propagation of ion cyclotron waves in a multicomponent cold plasma. Obviously, measurements can be made only in thc prcsence of ion cyclotron wave energy which occurs in the Pcl?2 geomagnctic pulsation frequency range (0.1?5 Hz).