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 feet 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.