Acceleration of oxygen ions in the dynamic magnetotail
The substorm-related acceleration and flux increases of energetic oxygen ions are studied on the basis of test particle orbits in the fields obtained from an MHD simulation of plasmoid formation and ejection and the collapse (dipolarization) of the inner tail. The simulated fluxes show large ani...
| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2004-04-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/22/1305/2004/angeo-22-1305-2004.pdf |
| Summary: | The substorm-related acceleration and flux increases of energetic
oxygen ions are studied on the basis of test particle orbits in the fields
obtained from an MHD simulation of plasmoid formation and ejection and the collapse
(dipolarization) of the inner tail. The simulated fluxes show large
anisotropies and nongyrotropic effects, phase bunching, and spatially and
temporally localized beams. The energy distribution of O<sup>+</sup> in the region of an
earthward beam in the near tail becomes significantly harder, more pronounced
than for protons, in qualitative agreement with observations. The simulation also
shows tailward beams of energetic O<sup>+</sup>ions closely associated with the passage
of a plasmoid, both inside the plasma sheet boundary and inside the central
plasma sheet, consistent with observations in the far tail. The acceleration at
the near-Earth x-type neutral line produces a narrow duskward beam of energetic
O<sup>+</sup> in the duskward extension of the x-line, which was not found to be as pronounced in
proton test particle simulations.<br><br>
<b>Key words.</b> Magnetospheric physics (energetic particles,
trapped; magnetotail; storms and substorms) |
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| ISSN: | 0992-7689 1432-0576 |