Variations of Pickup Ion Distributions and their Relation to Interplanetary Conditions and Waves

Abstract

Pickup ion distributions vary substantially on a variety of time scales, although their sources may be relatively steady. This complicates their use as probes of the heliospheric and local interstellar particle populations. Interstellar He+ pickup ion observations from SOHO/CTOF and measurements of interplanetary conditions from SOHO and WIND enable a quantitative statistical analysis of these variations. Pickup ion distributions have been shown to correlate with IMF orientation, solar wind density, and IMF strength. Correlations of the pickup ions with IMF fluctuations are demonstrated, and it is shown that these are consistent with pitch angle scattering by waves. Further questions in pickup ion flux variations are discussed.