Abstract

Magnetospheric ULF waves at Pc-5 (mHz) frequencies may have profound effects on relativistic electron fluxes in the outer radiation belts by driving radial diffusion, a process which may either deplete the belts of electrons by allowing electrons to drift outward through the stable trapping bound... Show moreMagnetospheric ULF waves at Pc-5 (mHz) frequencies may have profound effects on relativistic electron fluxes in the outer radiation belts by driving radial diffusion, a process which may either deplete the belts of electrons by allowing electrons to drift outward through the stable trapping boundary, or increasing the overall energy content of the belts through inward radial diffusion and energization of energetic electrons. The energy for most global-scale Pc-5 activity results from the driving action of the solar wind, either through shear interactions at the magnetopause flanks, or directly through pressure or IMF variations embedded in the background solar wind. However, the relationship between ULF power at a given point in the magnetosphere and the driving power of the solar wind is not simple: as a wave propagates through the magnetosphere, partial reflections from Alfven gradients, magnetospheric field line resonances, and global cavity modes may all act to either enhance or suppress wave power at a given frequency and location in space. In this effort we use global MHD simulations of the magnetosphere/solar wind interaction to probe the mapping function of fluctuations in the solar wind into Pc-5 ULF power in the inner magnetosphere and radiation belts. Broadband variations in solarwind conditions are imposed, and the resulting ULF activity in the magnetosphere characterized as a function of frequency and location. This ULF activity may then be used to characterize radial transport rates in the radiation belts in terms of relevant diffusion coefficients. By comparing the ULF power distribution in the magnetosphere during events driven by observed solar wind conditions to those characterized by our broadband mapping, we investigate the feasibility of empirically modeling magnetospheric ULF wave activity as it relates to ULF power in the solar wind. Show less