Survey of magnetosonic waves and proton ring distributions in the Earth's inner magnetosphere

Abstract

Fast magnetosonic waves can lead to the local acceleration of electrons from ∼10 keV up to a few MeVon a timescale of 1-2 d and may play an important role in radiation belt dynamics. Here we present a survey of wave and particle data from the Combined Release and Radiation Effects Satellite (CRRES) to determine the global morphology of the waves as a function of magnetic activity, and to investigate the role of proton rings as a potential source mechanism. The intensity of fast magnetosonic waves in the frequency range 0.5 fLHR < f < 30 keV) with energies exceeding the Alfvén energy (ER > EA) required for instability closely matches the distribution of magnetosonic waves on the dusk side, both inside and outside the plasmapause, suggesting that low energy proton rings are a likely source of energy driving the waves. However, intense magnetosonic waves are also observed outside the plasmapause on the dawn-side that do not satisfy (ER > EA). Although proton rings with ER > 30 keV could drive the instabilities, the source of these waves is yet to be properly identified. Since fast magnetosonic waves can accelerate electrons we suggest that they may provide a significant energy transfer process between the ring current and the outer electron radiation belt. Copyright 2008 by the American Geophysical Union.