LOW-ENERGY UPFLOWING ION EVENTS OBSERVED BY EXOS-D - INITIAL RESULTS

Initial observations of low-energy upflowing ion events from the Suprathermal Ion Mass Spectrometer (SMS) on EXOS-D are presented. The SMS instrument on EXOS-D measures the mass composition, energy and angular distributions of thermal and suprathermal ions in the 0.1-4000 eV/q energy-per-charge and 0.8-70 amu/q mass-per-charge ranges. Two events are examined. The first features predominantly conical ion pitch-angle distributions and the second has mainly field-aligned distributions. Both events displayed small scale variations in upward flux, composition, and angular characteristics, and coincided with small-scale magnetic field fluctuations. In both events, the peak He+ and H+ fluxes were comparable; the O+ flux was a factor of 5-10 larger. The pitch-angle distribution often switched rapidly between field-aligned and conical.