Evidence for Nonadiabatic Oxygen Energization in the Near‐Earth Magnetotail From MMS

Abstract

AbstractWe present Magnetospheric Multiscale (MMS) mission observations of substorm‐related ion injections at magnetotail positions between ∼7.5 RE and 8.5 RE. Energization of supra‐thermal ions (50 keV–1,000 keV) is strongly species dependent, with oxygen reaching significantly higher peak energies than protons. Using a previously established correlation technique, we confirm that the highest energy (>400 keV) oxygen ions are multiply charged of solar wind origin, enabling them to reach high energies in rough proportion to their charge states. Significantly, we conclude that oxygen ions between 130 keV and 330 keV are singly charged, and that they sometimes achieve higher energizations relative to protons, that is, higher than expected based on their charge states. We conclude that nonadiabatic processes can boost the energies of the oxygen ions. The technique does not depend on “before injection” and “after injection” spectral comparisons, and therefore likely represents the most definitive test yet of nonadiabaticity.