The elemental composition in energetic particle events at high heliospheric latitudes

The relative abundances of low energy ions (0.6-2.0 MeV/n) in solar energetic particle and corotating interaction region (CIR) events have been measured by the EPAC experiment aboard Ulysses since launch in October 1990 until the present time. We give an overview of the abundances of heavy ions (He, C, Ne, Fe) relative to oxygen during energetic particle events lasting longer than 5 d during the in- and out-of-ecliptic phase of the mission. While the period October 1990 to August 1992 was dominated by high solar activity the Ulysses out-of-ecliptic passage at solar latitudes up to 45 deg went parallel to the declining phase of solar activity. Thus very clear structure of cotorating interaction regions was observed. While the in-ecliptic composition is in general agreement with measurements made near the Earth, the development of the CIR composition shows two phases: from August 1992 to May 1993 the C/O-ratio is 0.55-0.70; afterwards it increases to 0.8-0.9. This increase is correlated to the disappearance of the current sheet at 30 deg solar latitude reported by Smith et al. (1993). (Author)