ULYSSES energetic ion observations during the declining phase of solar cycle 22

Abstract

The Ulysses spacecraft was launched in October 1990, just after the maximum of solar cycle 22. Part of the journey to Jupiter was during one of the most active periods of solar activity recorded so far. Solar activity remained exceptionally high for many months after launch, solar energetic particles dominating the particle observations at Ulysses. The slow decline in solar activity which followed continued on past the encounter with Jupiter in February 1992. By July of 1992 the level of solar activity had declined to such an extent that the energetic ions being observed at Ulysses were associated predominantly with recurrent co-rotating interaction regions. This behaviour continued throughout the rest of 1992 and through almost all of 1993. Towards the end of 1993 and on into 1994, as Ulysses climbed to higher latitudes, there was evidence of a slow decline in the peak intensity seen during the recurrent events. We present the latest observations of energetic ions as Ulysses reached the high-latitude south polar region of the Heliosphere.