The nature of the variability of wave particle interactions in the inner magnetosphere and consequences for diffusion models

Abstract:

Changes in electron flux in Earth's outer radiation belt are often modeled using a reduced physics-based framework based on diffusion. Diffusion coefficients for such models can be constructed from parameterized statistical wave models and idealized plasma and magnetic field properties. We demonstrate the amount of variability in the strength of pitch-angle diffusion due to plasmaspheric hiss in Earth’s magnetosphere, both in the outer radiation belt and in the slot region. The timescales of variability are constrained with Van Allen Probe observations. We use a stochastic parameterization scheme to investigate the consequences of that variability in a diffusion model. The timescales of variability of the wave-particle interactions are constrained using Van Allen Probe observations. The results from the stochastic parameterization are contrasted with the standard approach of constructing averaged diffusion coefficients. The median rate of diffusion depends upon the timescale of variability of the wave-particle interactions, and the variability of the resulting ensemble is greatly enhanced for longer timescales of variability.