Method for direct detection of pitch angle scattering caused by plasma waves

We propose a new method to directly detect pitch angle scattering of energetic particles caused by plasma waves in space plasma. The Wave-Particle Interaction Analyzer (WPIA), a new instrument proposed by [1], measures the energy exchange from waves to particles. In this study, we expand its applicability to detect pitch angle scattering of resonant particles by plasma waves by calculating g values. g value is defined as the accumulation value of the Lorentz force acting on each particle and indicates the lost momentum of waves. We apply the proposed method to the results of a one-dimensional electron hybrid simulation reproducing the generation of whistler-mode chorus emissions around the magnetic equator [2, 3]. Using the wave and particle data obtained at fixed observation points assumed in the simulation system, we conduct a pseudo-observation of the simulation result using the WPIA and analyze the g values. Our analysis yielded significant values indicating the strong pitch angle scattering for electrons in the kinetic energy and pitch angle ranges satisfying the cyclotron resonance condition with the reproduced chorus emissions. The results of this study demonstrate that the proposed method enables us to directly and quantitatively identify the location at which pitch angle scattering occurs in the simulation system and that the method can be applied to the results of space-based observations by the Exploration of energization and Radiation in Geospace (ERG) satellite.