Injection and propagation of solar protons to high heliospheric latitudes: Ulysses Ket observations Original Research Article

The Ulysses spacecraft at high heliographic latitudes has detected eight large solar energetic particle events during the recent solar maximum in 2000 and 2001 years. These events are easily identified with famous episodes of the solar activity and the corresponding SEP events near the Earth. Analyzing the absolute intensities of ∼40–100 MeV proton time profiles from the Ulysses COSPIN/KET and the GOES detector near Earth we find that for these eight events the intensities vary only within a factor of 2–3 from event to event at high latitudes during the first 30 h. In contrast the intensities at Earth differ from one event to another by several orders of magnitude. Thus, the time history during these 30 h has only a weak dependence on the relative position of Ulysses to the possible flare location. This implies: (1) a nearly isotropic injection of protons with comparable intensities to high heliolatitudes, and (2) a similar propagation process during the first 30 h of the events. We attribute the fact that the decay phases of these events are nearly the same at Ulysses and in the ecliptic rather to cross-field diffusion than to the presence of a shock.