Radial Transport due to ULF Field Line Resonances and Cavity Modes in the Inner Magnetosphere

Abstract:

It is well known that ULF waves can play a major role in the radial transport and energization of ions and relativistic electrons in the inner magnetosphere. Such radial transport is often described in terms of a quasi-linear radial diffusion coefficient. However, ULF waves in the inner magnetosphere are often observed in the form of discrete modes such as field line resonances and plasmaspheric cavity modes. Such discrete modes violate the assumption of broad-band turbulence inherent in quasi-linear theory. We have developed a ULF wave code that can model such modes in the inner magnetosphere, including a distributed ionosphere and plasmasphere. This code can model waves at lower L-shells and higher frequencies than full global MHD models. In addition, we have developed a test particle simulation that can follow the particle transport and acceleration in the wave fields of the ULF wave code using both a guiding center approach and a full Lorentz force solver. Using these coupled codes, together with observations from the Van Allen Probes, we will investigate the hypothesis that radial transport in the inner magnetosphere is often non-diffusive.