A COMPARISON OF RECURRENT ENERGETIC ION ENHANCEMENTS OBSERVED AT ULYSSES AND AT 1-AU BY IMP-8 AND SAMPEX - ULYSSES LAUNCH UNTIL FOLLOWING THE FIRST NORTH POLAR PASSAGE

During the Ulysses mission, the Goddard Space Flight Center instrument on IMP 8 and the University of Maryland low energy ion composition an alyzer instrument on SAMPEX observed recurrent MeV/amu ion enhancement s in the ecliptic plane at 1 AU. We identify those IMP 8/SAMPEX events related to the recurrent events observed at Ulysses from its launch u ntil mid-1996, following the first passage over the north solar pole, and compare their properties. Two types of recurrent events were prese nt at Earth. Recurrent enhancements of particles streaming sunward fro m CIRs in the outer heliosphere were observed most clearly at Earth af ter the Ulysses Jupiter encounter. Most of the CIRs/particle enhanceme nts at Ulysses, even at high heliolatitudes, can be associated with re current events/high-speed streams at Earth by considering simple corot ation delays. This suggests that the events at high latitudes occurred poleward of equatorward extensions of the polar coronal holes which p roduced corotating high-speed streams in the ecliptic. The association between events at Ulysses and Earth was less clear in 1996 when there were few major streams from polar coronal hole extensions present nea r the ecliptic. At the furthest distance of Ulysses from the Sun (5.4 AU), the intensity of similar to 1 MeV/amu ions in CIR-associated even ts was 1-2 orders of magnitude higher than at Earth. The intensity at Ulysses then declined as the spacecraft moved closer to the Sun and to high latitudes to reach < 0.1% of that at Earth near polar passage. T he observations confirm that the decrease in the intensity of corotati ng events at high latitudes was predominantly due to the changing spac ecraft latitude rather than to a temporal decline in the intensity of corotating events throughout the heliosphere. We suggest that some of the north-south asymmetries in the particle events observed by Ulysses at high latitudes may be associated with differences in the solar win d structure and energetic particle events at low latitudes observed at Ulysses and at Earth during the second half of 1991 were associated w ith solar activity which, over a period of several solar rotations, wa s largely confined to a limited range in Carrington longitude.