Pronounced enhancements of pickup hydrogen and helium in high-latitude compressional regions

Abstract

Pickup hydrogen and helium distributions are measured in compressive corotating regions at high heliographic latitudes. The enhancements can be explained using a pickup ion transport model which includes compression but requires a long scattering mean free path. The long mean free path is generally observed for pickup ions at high latitudes, but it is not explained by current theories of wave-particle interaction. The fact that the mean free path is not reduced in the high-latitude compressed events suggests that the long mean free path is not isolated to highly static solar wind conditions. It also has important implications for wave-particle interaction theories since the turbulence within the compressed events is expected to be qualitatively different from the turbulence in static noncompressed solar wind.