Use of pitch angle dependence of flux oscillations as a diagnostic tool for determining the spatial structure of oscillations

Abstract

Waves and instabilities in the ULF range make crucial contributions to processes that transfer energy from the solar wind into to the magnetosphere and produce geo-space events like geomagnetic storms and sub-storms. While ULF waves are known to efficiently energize and transport relativistic electrons through resonant interactions leading to radial diffusion, their global structure, occurrence and characteristics are not well understood. At the same time use of realistic spectral characteristics and structure of the ULF waves are required for determination of rate of diffusion of relativistic electrons via drift resonance. We show here that pitch angle structure of energetic particle fluctuations can be used to determine the structure of the ULF oscillations along the field lines through the use of multivariate analysis techniques. Using AMPTE CCE particle data, we use variations of the principle component analysis to examine the technique.