Energetic oxygen: A direct coupling mechanism between the magnetosphere and thermosphere

This study investigates the effects of the precipitation of energetic O+ ions (0.7 – 12 keV) into the atmosphere during magnetic storms. The energetic O+ ion flux produces a splash of lower energy neutral oxygen atoms at the top of the atmosphere. As a result of the photo‐ionization and charge exchange with H+ ions in the plasmaspherethese backscattered atoms produce a low energy O+ flux that is more than 10 times larger in magnitude than the original energetic O+ flux. The energetic O+ events thus provide a potential source mechanism for the lower energy (≲30 eV) O+ ions observed in the plasmasphere. We also suggest that the energetic ion events may be self‐sustaining in that some of the ionized ‘splash’ particles (≲10%) are subsequently accelerated by an as yet unidentified mechanism to the higher observed energies. We find that 96% of the incoming energy is transferred to the neutral atmosphere in the form of heating. Measured fluxes indicate heating rates as high as ∼0.4 ergs cm−2sec−1ster−1.