New Chorus Diffusion Coefficients for Radiation Belt Modelling

Whistler mode chorus is an important magnetospheric wave emission playing a major role in radiation belt dynamics, where it contributes to both the acceleration and loss of relativistic electrons. In this study we compute bounce and drift averaged chorus diffusion coefficients for 3.0 < L* < 6.0, using the TS04 external magnetic field model, taking into account co-located near-equatorial measurements of the wave intensity and fpe/fce, by combining the Van Allen probes measurements with data from a multi-satellite VLF wave database. The variation of chorus wave normal angle with spatial location and fpe/fce is also taken into account. We find that chorus propagating at small wave normal angles has the dominant contribution to the diffusion rates in most MLT sectors. However, in the region 4 <= MLT < 11 high wave normal angles dominate at intermediate pitch angles. In the region 3 < L* < 4, the bounce and drift averaged pitch angle and energy diffusion rates during active conditions are primarily larger than those in our earlier models by up to a factor of 10 depending on energy and pitch angle. Further out, the results are similar. We find that the bounce and drift averaged energy and pitch angle diffusion rates can be significantly larger than the new model in regions of low fpe/fce,eq, where the differences can be up to a factor of 10 depending on energy and pitch angle. Funding was provided by the Natural Environment Research Council (NERC) Highlight Topic grant NE/P01738X/1 (Rad-Sat) and the NERC grants NE/V00249X/1 (Sat-Risk), NE/R016038/1 and NE/X000389/1.