On the interaction of solar near-relativistic electrons with back-scatter regions beyond 1 AU

Abstract

We study the near‐relativistic (NR; >30 keV) electron event observed on 2000 February 18 by the Advanced Composition Explorer spacecraft. Highly collimated pitch‐angle distributions were observed during the first ∼2 h of the event. Roel of (2008) explained this event by assuming that the propagation of NR electrons is essentially “scatter‐free” in the inner heliosphere and that beyond 1 AU, particles are “back‐scattered” by magnetic field compressions and irregularities. We use Monte Carlo simulations to explore this approach. We fit observational sectored intensities to assure that the directional information contained in the data is used in full. We conclude that the event cannot be explained without assuming a back‐scatter region beyond 1 AU and that NR electrons propagated under weak‐scattering conditions in the inner heliosphere.