Thermal Oxygen Surges in Earth's Inner Magnetosphere During Geomagnetic Storms
Thursday, October 1, 2015
Jörg-Micha Jahn, Southwest Research Inst, San Antonio, TX, United States, Ruth M Skoug, Los Alamos Natl Lab, Los Alamos, NM, United States, Brian Larsen, The New Mexico Consortium, Los Alamos, NM, United States, Reeves Geoffrey, Los Alamos National Laboratory, Los Alamos, NM, United States and Harlan E. Spence, University of New Hampshire Main Campus, Space Science Center, Durham, NH, United States
Abstract:
Ionospheric oxygen plays in important role in the dynamics of Earth’s magnetosphere. After emerging from the ionosphere and entering the plasma sheet, it participates in the dynamics and the energization processes that magnetospheric plasma undergoes during quiet and disturbed times. Its greater mass (compared to hydrogen) may have an impact on tail reconnection processes that drive the dynamics of the inner magnetosphere. Once energized and injected into Earth’s ring current at energies of 10’s to 100’s keV, oxygen has a well-known impact on the energy content of the ring current during geomagnetic storms. A second population of terrestrial oxygen forms the oxygen torus, a cold (< 50 eV) population hugging the outer boundary of Earth’s plasmasphere. It also occurs associated with geomagnetic storms. The torus is caused by direct access of ionospheric oxygen into the inner magnetosphere. In this paper we report occurrence of a third oxygen population associated with geomagnetic storms. With the two Van Allen Probes spacecraft covering the inner magnetosphere from plasmaspheric altitudes to just inside geosynchronous orbit we observe a warm (50 eV to 1 keV) population of oxygen ions occurring shortly (within 6 hours) after the onset of many geomagnetic storms. This population completely fills the region outside the plasmasphere, often reaching to geostationary L-shells. This populstion is long-lived, being present for many hours up to multiple days. Oxygen fluxes in this region are sufficiently high that the warm oxygen density reaches or exceeds the density of protons.
