O <sup>+</sup> Ion Conic and Plasma Sheet Dynamics Observed by Van Allen Probe Satellites during the 1 June 2013 Magnetic Storm

TitleO + Ion Conic and Plasma Sheet Dynamics Observed by Van Allen Probe Satellites during the 1 June 2013 Magnetic Storm
Publication TypeJournal Article
Year of Publication2016
AuthorsBurke, WJ, Erickson, PJ, Yang, J, Foster, J, Wygant, J, Reeves, G, Kletzing, C
JournalJournal of Geophysical Research: Space Physics
Date Published05/2016
Keywordsoxygen ion conics; plasma sheet dynamics; Van Allen Probes
AbstractThe Van Allen Probe satellites were near apogee in the late evening local time sector during the 1 June 2013 magnetic storm's main phase. About an hour after crossing the ring current's “nose structure” into the plasma sheet, the satellites encountered a quasi-periodic sequence of 0.08 - 3 keV O+ ions. Pitch angle distributions of this population consistently peaked nearly anti-parallel to the local magnetic field. We interpret this population as O+ conics originating in the northern ionosphere. Sequences began as fairly steady state conic fluxes with energies in the ~ 80 to 100 eV range. Over about a half hour build-up phase, O+ energies peaked near 1 keV. During subsequent release phases lasting ~ 20 minutes, O+ energies returned to low-energy starting points. We argue these observations reflect repeated formations and dissolutions of downward, magnetically aligned electric fields (ε||) layers trapping O+ conics between mirror points within heating layers below and electrostatic barriers above [Gorney et al., 1985]. Nearly identical variations were observed at the locations of both satellites during 9 of these 13 conic cycles. Phase differences between cycles were observed at both spacecraft during the remaining events. Most “build-up” to “release” phase transitions coincided with AL index minima. However, in situ magnetometer measurements indicate only weak dipolarizations of tail-like magnetic fields. The lack of field-aligned reflected O+ and tail-like magnetic fields suggest that both ionospheres may be active. However, southern hemisphere origin conics cannot be observed since they would be isotropized and accelerated during neutral sheet crossings.
URLhttp://doi.wiley.com/10.1002/2015JA021795
DOI10.1002/2015JA021795
Short TitleJ. Geophys. Res. Space Physics


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