Nonlinear Wave-particle Interactions In The Inner Magnetosphere

In the inner magnetosphere,there are various kinds of plasma waves.These waves can resonate with different species of charged particles with different energies,causing equatorial pitch-angle and energy scattering,and affecting the distribution function of particles.Quasi-linear theory is often used to describe the wave-particle interaction,but we find the interaction between EMIC waves and charged particles will be highly nonlinear in the storm time.Thus,we map out the regions of nonlinear interaction with dimensionless parameter R,and analyzing the trajectories of resonant particles in different situations through test-particle simulation.In this paper,we investigate the nonlinear interaction of ring current protons,oxygen ions and radiation belt electrons with three different bands of EMIC waves(H+ band waves,He+ band waves and O+ band waves),and studying the influence of background plasma conditions on the nonlinear regions.We find the region of nonlinear interaction becomes larger,when the angular frequency of the EMIC wave is closer to the particle grofrequency.The increase of magnetic shell L,background electron density and the density of plasmas ion in the storm time also have a positive influence on nonlinear behavior.Compared with He+ band waves and O+ band waves,protons and electrons are more likely to interact with H+ band waves nonlinearly.Nonlinear interactions contain phase trapping and phase bunching,and these two interactions have opposite influences on energetic particles.Phase trapping of oxygen ions with O+ band waves causes the spiral development of oxygen ions energy,which has not been reported before.In addition,we investigate the interaction of Chorus and Hiss with radiation belt electrons,and find nonlinear interactions still occur.The conclusions show that nonlinear wave-particle interactions in the inner magnetosphere are complex,and the effects of nonlinear interacitons are different according to the species of particles and waves.These nonlinear interactions can affect the distribution of particles in the inner magnetosphere strongly,which is differernt from the quasi-linear theory.