Sensitivity of Phase Space Density Evolution to Event-Specific Diffusion Coefficients

Abstract:

The evolution of the radial phase space density profile of energetic electrons in the outer zone radiation belts depends explicitly on the prevailing balance of local heating, radial transport, and particle loss to the magnetopause and atmosphere. In particular, the intensity and distribution of whistler-mode chorus waves in the magnetosphere can lead to local peaks in the radial profile of the phase space density, diffusing particles from low-energy, high density regions of phase space to the keV and MeV energies commonly observed in the outer zone. The K2 modeling framework combines Stochastic Differential Equation (SDE) methods with global, 3d MHD/test particle simulations to provide a comprehensive view of the temporal and spatial evolution of the radiation belts in response to event-specific local heating and loss as specified by chorus-induced local diffusion, along with self-consistent radial transport via MHD waves and impulses. In this work we examine the effect of varying distributions and intensities of whistler-mode chorus on the production of characteristic radial phase space density peaks, and discuss the contribution of radial transport processes and magnetopause loss in the overall evolution of the outer zone electron distribution function.