26-day analysis of energetic ion observations at high and low heliolatitudes: Ulysses and ACE

We present observations of energetic (0.34-8 MeV) ions from the Ulysses spa cecraft during its second ascent to southern high latitude regions of the h eliosphere. We cover the period from January 1999 until mid-2000 as Ulysses moved from 5.2 AU and 18 degrees S to 3.5 AU and 55 degrees S. In contrast to the long-lived and well-defined similar to 26-day recurrences that were observed throughout Ulysses' first southern pass, energetic ion fluxes dur ing the first portion of the Ulysses' second polar orbit are highly irregul ar. Although corotating interaction regions (CIRs) are clearly present in s olar wind and magnetic field data throughout the first half of 1999, their effects on energetic ion intensities are quite different from what they wer e in 1992-1993. No dominant strictly recurrent ion flux increases are obser ved in association with the arrival of these CIRs. Correspondingly, there i s no stable structure of large polar coronal holes during the same period. Isolated transient solar energetic particle (SEP) events are observed at lo w and high latitudes. We compare energetic ion observations from the ACE an d Ulysses spacecraft during the first half of 1999 to determine the influen ce of these SEP events in the observed recurrent CIR structure. Such SEP ev ents occurred only occasionally during 1992-1993, but when they occurred, t hey obscured the recurrences in a manner similar to that observed in 1999-2 000. We therefore conclude that the basic differences in the behavior of en ergetic ion events between the first and second southern passes are due to the short life of the corotating structure and the higher frequency of SEP events occurring in 1999-2000.