This grant will support a three-year study of plasma instabilities associated with magnetic pulsations in the magnetosphere. The purpose of the study is to conduct data analyses, analytical calculations and computer simulations for a better understanding of wave modes, generation mechanisms, field- aligned mode structures and ion heating phenomena. Wave excitation mechanisms for various wave modes including stormtime Pc 5 waves and auroral hiss have been studied. This study will focus on stormtime Pc 5 waves on the equatorial plane and Pc 3 magnetic pulsations in the polar cusps. Stormtime Pc 5 waves are large amplitude quasi-sinusoidal magnetic field oscillations with period in the range of 150-500 seconds. One popular mechanism for explaining stormtime Pc 5 waves is the drift mirror instability. Recent study indicates that the instability condition for the drift mirror instability was not satisfied for one stormtime Pc 5 wave event. This important result raises a fundamental question about the instability mechanism for stormtime Pc 5 waves. In addition, this grant will extend the investigation of magnetic pulsations to other regions. In particular, plasma instabilities associated Pc 3 waves recently detected at mid-altitudes by DE-1 will be studied. The free energy sources for cusp magnetic pulsations are not known and need to be examined theoretically. One key element of the grant is that the observed distribution function will be used for investigating plasma instabilities associated with magnetic pulsations. Spacecraft plasma data have been obtained for that purpose.
