Radial Diffusion of Planetary Radiation Belts' Particles by Fluctuations with Finite Correlation Time

Radial diffusion in planetary radiation belts is a dominant transport mechanism resulting in the energization and losses of charged particles by large-scale electromagnetic fluctuations. In this study, we revisit the radial diffusion formalism by relaxing the assumption of zero correlation time in the spectrum of fluctuations responsible for the transport of charged particles. We derive a diffusion coefficient by assuming fluctuations that (1) are time homogeneous, (2) too small to trap the particles, and (3) can decorrelate on timescales comparable to the transit time of the particles. We demonstrate through self-similar solutions of the Fokker-Planck equation that autocorrelation time tc much larger than the linear transit time/particle drift period tau(L) = WL D1 results in characteristic time for transport independent of the drift frequency and faster than for short correlation time. In both instances, that is for short (t(L)>> t(c)) and long (t(L) similar to t(s), with s