Incorporating spectral characteristics of Pc5 waves into three‐dimensional radiation belt modeling and the diffusion of relativistic electrons

Abstract

The influence of ultralow frequency (ULF) waves in the Pc5 frequency range on radiation belt electrons in a compressed dipole magnetic field is examined. This is the first analysis in three dimensions utilizing model ULF wave electric and magnetic fields on the guiding center trajectories of relativistic electrons. A model is developed, describing magnetic and electric fields associated with poloidal mode Pc5 ULF waves. The frequency and L dependence of the ULF wave power are included in this model by incorporating published ground‐based magnetometer data. It is demonstrated here that realistic spectral characteristics play a significant role in the rate of diffusion of relativistic electrons via drift resonance with poloidal mode ULF waves. Radial diffusion rates including bounce motion show a weak pitch angle dependence for αeq ≥ 50° (λ ≤ 20°) for a power spectral density which is L‐independent. The data‐based model for greater power at higher L values yields stronger diffusion at αeq = 90°. The L6 dependence of the diffusion coefficient which is obtained for a power spectral density which is L‐independent is amplified by power spectral density which increases with L. During geomagnetic storms when ULF wave power is increased, ULF waves are a significant driver of increased fluxes of relativistic electrons inside geosynchronous orbit. Diffusion timescales obtained here, when frequency and L dependence comparable to observations of ULF wave power are included, support this conclusion.