[PEM13-P19] Oxygen-proton differences in ion energies dominating plasma pressure: Dependence on storm phases and solar wind drivers
Keywords:Magnetic storms, Substorms, RIng current, Oxygen ions, Ion transport and acceleration
The present study extends this analysis toward a larger database obtained from a longer period of magnetic storm times including the recovery phase. We also compare mass-dependent/selective energization between different solar wind drivers such as coronal mass ejections and corotational interaction regions. We primarily use data from the MEP-i (Medium-Energy Particle experiments - ion mass analyzer) on board the Arase spacecraft. MEP-i measures ions with energies of 10 to 180 keV/q and distinguishes between different ion species. Arase observed the nightside near-Earth magnetosphere (L<10) during 7 CME-driven and 7 CIR-driven storms with the Dst minimum of smaller than -50 nT in Years 2017 and 2018. The dependence on storm phases and solar wind drivers helps identify magnetospheric conditions favorable for mass-dependent/selective acceleration and in turn provides clues for understanding important physical mechanisms. Utilizing observations made by the MMS spacecraft in the near-Earth plasma sheet, we also compare oxygen-to-proton differences inside earthward bursty bulk flows with the Arase/MEP-i observations. The multi-spacecraft observations help better understand the temporal evolution of the mass-dependent/selective acceleration processes.