Cospin let observations of recurrent energetic particle events during the in-ecliptic phase of the Ulysses mission

Abstract

The Ulysses spacecraft, launched in October 1990, traversed the in-ecliptic region of the heliosphere from 1 to 5 AU during the post-maximum phase of solar cycle 22 prior to its encounter with Jupiter in February 1992. In the period from launch up to mid-1991, particle events were dominated by the effects of large-scale transient structures in the solar wind. Thereafter, a more regular pattern of recurrent events related to Corotating Interaction Regions (CIR) evolved. We present an overview of these CIR-related events as recorded by the Low Energy Telescope (LET), part of the COSPIN experiment on board Ulysses, in the energy range ~ 1 to 20 MeV/n, with particular emphasis on the composition of the particle populations.