Differential flow: Locally Generated or Coronal Artifact?

Abstract:

Alpha particles and proton beams differentially flow in the solar wind with respect to the proton core by about an Alfvén speed. Whether differential flow is an artifact of coronal physics or a signature of local acceleration as the solar wind propagates earthward is undetermined. A new analysis of Wind spacecraft observations in the solar wind combines Faraday Cup ion distribution functions with vector magnetic field measurements to characterize the bulk properties of the proton core, proton beam, and alpha particles with 92s time resolution. We utilize this data set to examine the occurrence of differential flow at 1 AU as a function of solar wind conditions and other parameters. We discuss the implications of observed trends on our understanding of differential flow’s origin.