Azimuthal Distribution of ULF Wave Power in the Magnetosphere

The Van Allen radiation belts contain highly energetic particles which interact with a variety of plasma and MHD waves. ULF waves play an important role in loss and acceleration of energetic particles. There is still much to be understood about the interaction between charged particles and ULF waves and how these waves influence diffusion of charged particles. We will investigate how ULF wave power distribution in azimuth affects radial diffusion of charged particles. We will present results from CRRES (Combined Release and Radiation Effect Satellite) magnetometer data study regarding the azimuthal distribution of wave power in the geomagnetic field. Current theoretical treatments of radial diffusion assume a constant power distribution in azimuth while our results show that this is clearly not the case. Our ongoing investigation includes further study of azimuthal distribution of wave power as well as the distribution of wave power across different mode numbers. In order to use the in situ point measurements such as from a spacecraft, it is necessary to assume that all of the wave power exists in the first mode. But how valid is this assumption? How much power is contained in the higher modes? These are some of the questions we wish to investigate as a part of our ongoing study to better our understanding of particle dynamics in the magnetosphere.