Ulysses particle observations of the March 1991 solar flare events

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Abstract
We present observations of energetic ions from the COSPIN instrument on the Ulysses spacecraft at 2.5 AU during the March 1991 series of solar flare events. The intensity profiles observed during this sequence of events were affected both by the presence of interplanetary shocks and large‐scale discontinuities in the magnetic field, the low‐energy (∼1 MeV) protons being influenced mainly by the shocks and the discontinuities, and the high‐energy (∼100 MeV) protons by the discontinuities.The first shock observed at Ulysses was followed by several discontinuities and a Coronal Mass Ejection (CME) which were probably moving with the shock. Particles following this shock were prevented from propagating freely into the heliosphere by the structure moving with the shock, and were carried along with it. A second shock was followed by a region containing bi‐directional particle anisotropies. A subsequent enhancement of low‐energy particles suggests the passage of another shock. This was followed by a slow intensity decay which coincided with a second CME and where bi‐directional particle anisotropies were again observed.

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