Low energy anomalous ions at northern heliolatitudes

Abstract

Measurements of the anomalous component of nitrogen, oxygen, and neon ions (∼0.5-8 MeV/nucl.) at northern heliolatitudes by the HI-SCALE instrument on the Ulysses spacecraft show that the energy spectra of these ions are essentially flat from the highest heliolatitudes (80° N) to near the ecliptic plane. For energies from 1-8 MeV/nucl., the northern hemisphere O fluxes are about a factor of two larger than those measured earlier at high southern latitudes. During ∼150 days (∼5 solar rotations) in late 1996, solar activity added low energy (∼0.5-1 MeV/nucl.) N, O, Ne, and Fe ions to the high latitude interplanetary medium. The northern hemisphere measurements are consistent with essentially no latitude gradient for particles in this energy range at this time. These results call into some question the importance of acceleration of anomalous cosmic rays of this energy by corotating interaction regions in the inner heliosphere.