Magnetospheric field fluctuations and the penetration of solar protons to low geomagnetic latitude

Abstract

Diffusive penetration of low energy solar protons into magnetospheric L shells below the limit of stable particle trapping is considered. Violation of the third adiabatic invariant by a wave-particle interaction involving a resonance at a low multiple of the particle drift period is suggested as the main cause of the diffusion. Azimuthal electric fields or azimuthal magnetic field gradients associated with very low frequency hydromagnetic waves bring about the motion in L.