Numerical modeling of multidimensional diffusion in the radiationbelts using layer methods

摘要

A new code using layer methods is presented to solve radiation belt diffusion equationsand is used to explore effects of cross diffusion on electron fluxes. Previous results indicatethat numerical problems arise when solving diffusion equations with cross diffusionwhen using simple finite difference methods. We show that layer methods, which are basedon stochastic differential equations, are capable of solving diffusion equations with crossdiffusion and are also generalizable to three dimensions. We run our layer code using twochorus wave models and a combined magnetosonic wave and hiss wave model (MH wavemodel). Both chorus and magnetosonic waves are capable of accelerating electrons toMeV levels in about a day. However, for the chorus wave models, omitting cross diffusionoverestimates fluxes at high energies and small pitch angles, while for the MH wave model,ignoring cross diffusion overestimates fluxes at high energies and large pitch angles.These results show that cross diffusion is not ignorable and should be included whencalculating radiation belt electron fluxes.