THE HIGH-LATITUDE PASS OF ULYSSES - ENERGETIC PARTICLE OBSERVATIONS WITH EPAC

We report on observations of energetic particles (EP) during the ascen t of ULYSSES to the south pole, on the fast pass from south to north a nd in the first few months after the north polar pass. After it left t he ecliptic plane the spacecraft moved periodically into a corotating (26 days period) fast solar wind stream and observed the accelerated E P associated with the forward and reverse shocks. Such particles were observed up to 68 degrees in heliographic latitude. Only when ULYSSES returned to lower latitudes did the accelerated beams reappear. The fa st pass from south to north polar regions showed on a compressed times cale similar features to those already observed on the ascending part. Apparently the recurrence period of the EP did not change throughout that pass. No evidence for differential rotation could be found in our data. The north polar pass again did not show energetic particles to be present at such high latitudes. In regions where the intensities we re low, we identified from the C/O ratio and oxygen spectrum an underl ying population of anomalous cosmic rays (ACR), which show a bidirecti onal field aligned anisotropy. The appearance of the EPs was anticorre lated to the modulated ACR and GCR fluxes. We conclude that ACR and GC R were modulated by the corotating interaction regions (CIR); shocks a ssociated with them accelerated the observed EP streams. During the fa st polar pass the latitudinal gradient of GCR protons was determined t o be 0.3 to 0.4%/degree.