Recurrences of interplanetary interaction regions at southern solar latitudes and approximate harmonics

Abstract

A series of low energy (~60 keV/nucl to several MeV/nucl) interplanetary particle enhancements was measured by the HI-SCALE instrument on the Ulysses spacecraft during the first approximately two-thirds of 1993. At this time Ulysses was located between ~4.3 - 5.0 AU and climbing from ~ 23 deg to ~40 deg south heliolatitude. Spectral analyses of the time series of the fluxes of protons, helium, CNO, and iron group ions in each of two energy intervals (>~0.5 keV/nucl) show that the fundamental rotation rate for the recurrent ion enhancements was ~26.5 days. At least six shorter periods were also found, not all of which were harmonics of the fundamental frequencies. These rotation rates are shorter than those of the interplanetary magnetic field and the solar source fields at this time.