Low energy charged particles in the high latitude heliosphere

Low energy ion and electron measurements made over the south and north polar regions of the sun by the HISCALE instrument on the Ulysses spacecraft during its solar minimum polar passages are summarized. The polar flux levels were considerably reduced in comparison to fluxes in the vicinity of the heliospheric current sheet. Flux variations with a period of ∼ 26 days were seen to nearly 80◦S but were not observed over the northern pole. Solar particle events originating from near-equatorial activity were seen at high southern latitudes, but not at high northern latitudes. Comparisons with in-ecliptic measurements made during the same time interval on the IMP8 spacecraft suggest that the polar differences are largely spatial and not temporal. The flux of low energy (∼ 0.8– 5.0 MeV/nucl) anomalous oxygen was measured to be ∼ 50% higher over the northern polar region than in the south. The flux of solar wind iron, measurable because of its convection into the instrument by the high speed polar solar wind, is estimated to be about a factor of two larger over the south pole than over the north.