Observations of Possible Injection of Interplanetary Oxygen into the Inner Magnetosphere
Tuesday, 16 December 2014
With the Advanced Composition Explorer's (ACE) Electron Proton and Alpha Monitor (EPAM) instrument being in a halo orbit about L1 and the Van Allen Probe's Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) instrument being in an eccentric orbit through the inner magnetosphere, the two instruments are situated perfectly for observing the inner magnetospheric response to energetic interplanetary particle events. Both instruments are designed to measure electrons and ions with energies between tens of keV and a few MeV, depending upon particle species. Using a new data analysis technique we've developed, the EPAM instrument can provide high energy-resolution, species-resolved energy spectra for a number of ion species including helium and oxygen which RBSPICE is designed to observe. Between May 22nd and 26th of 2013, EPAM observed an energetic particle event with a nearly flat energy spectra and greatly enhanced helium and oxygen composition. RBSPICE measured a strong surge in oxygen flux, but saw no correspondingly strong increase in the helium flux. We present a detailed analysis and comparison of the energetic ion spectra, composition, and timing measured by the ACE and the Van Allen Probes instruments in conjunction with magnetic field and energetic particle measurements from other spacecraft for this event, and provide a discussion on the injection of interplanetary oxygen into the inner magnetosphere.