Propagation of Energetic Particles to High Latitudes

Abstract

We present observations of energetic particles in the energy range ~1 MeV to ~100 MeV made by the COSPIN instrument on board the Ulysses spacecraft during the recent second northern polar pass. For a short time during this pass the Ulysses spacecraft was at high heliographic latitude, above the current sheet, and immersed in high-speed solar-wind flow coming from the northern polar coronal hole. Four large solar energetic particle events were observed. We discuss the solar conditions prevalent during the Ulysses mission, and in particular the conditions during this polar pass. We discuss the rise to maximum of these events and examine the onset time and the anisotropy of the energetic particles. We find that during these events the particle angular distributions were almost isotropic, but with a net outward flow along the magnetic field lines. We conclude that particles reached these high latitudes travelling along the magnetic field lines.