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Energized oxygen in the magnetotail : Current Sheet Bifurcation from Speiser motion
  • Don George,
  • Jorg-Micha Jahn
Don George
Southwest Research Institute

Corresponding Author:degeorge@swri.edu

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Jorg-Micha Jahn
Southwest Research Institute
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Oxygen ions can be a major constituent of magnetospheric plasma, yet the role of oxygen in the magnetosphere is often not sufficiently understood. We examine the case of a thinning current sheet prior to the onset of magnetic reconnection. We perform 2.5D PIC simulations of a 3-species system of electrons, protons and heavy ions ($O^+$). We initiated the simulations using the well-known GEM Challenge configuration. Our approach differs from previous simulations involving heavy ions in two important aspects. First, we initiate the simulations with energized $O^+$ as opposed to using a thermal population. The energization is based on published in-situ measurements consisting of an initial dusk-ward velocity equivalent to $\sim$7 KeV. Second, we tracked the particles directly in the simulation rather than performing test particle tracing in post processing. We show three main results. First, energized dawn-dusk streaming ions exhibit sustained Speiser motion. Second, a single population of heavy ions can produce a stable bifurcated current sheet. Third, magnetic reconnection is not required to produce a bifurcated current sheet.
Feb 2020Published in Journal of Geophysical Research: Space Physics volume 125 issue 2. 10.1029/2019JA027339