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Abstract We present multi‐platform observations of plasma cloak, O+ outflows, kinetic Alfven waves (KAWs), and auroral oval for the geomagnetic storm on 17 March 2015. During the storm's main phase, we observed a generally symmetric equatorward motion of the auroral oval in both hemispheres, corresponding to the plasmasphere erosion and inward motion of the plasma sheet. Consequently, Van Allen Probes became immersed within the plasma sheet for extended hours and repeatedly observed correlated KAWs and O+ outflows. The KAWs contain adequate energy flux toward the ionosphere to energize the observed outflow ions. Adiabatic particle tracing suggests that the O+ outflows are directly from the nightside auroral oval and that the energization is through a quasi‐static potential drop. The O+ outflows from the nightside auroral oval were adequate (‐ #/‐s) and prompt (several minutes) to explain the newly formed plasma cloak, suggesting that they were a dominant initial source of plasma cloak during this storm.
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Assessing the Sources of the O + in the Plasma Sheet
Abstract To study the average contributions of the cusp outflow through the lobes and of the nightside auroral outflow to the O+in the plasma sheet (PS), we performed a statistical study of tailward streaming O+in the lobes, plasma sheet boundary layer|the plasma sheet boundary layer (PSBL) and the PS, using MMS/Hot Plasma Composition Analyzer (HPCA) data from 2017 to 2020. Similar spatial patterns illustrate the entry of cusp‐origin O+from the lobes to the PS through the PSBL. There is an YGSM‐dependent energy pattern for the lobe O+, with low‐energy O+streaming closer to the tail center and high energy (1–3 keV) O+streaming near the flanks. Low energy (1–100 eV) O+from the nightside auroral oval is identified in the near‐Earth PSBL/PS with high‐density (>0.02 cm−3), and energetic (>3 keV) streaming O+with similar density (∼0.013 cm−3) is observed further out on the duskside of the PSBL/PS. The rest of the nightside auroral O+in the PSBL is mixed with O+coming in from the lobe, making it difficult to distinguish the source. We estimated the contributions of the different sources of H+and O+ions through the PS between 7 and 17 RE, using estimates from this work and data extracted from previous studies. We conclude that, during quiet times, the majority of the near‐Earth PS H+are from the cusps, the polar wind and Earthward convection from the distant tail. Similarly, while the O+in the same region has a mixed source, cusp origin outflow provides the highest contribution.
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- PAR ID:
- 10533237
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Space Physics
- Volume:
- 129
- Issue:
- 8
- ISSN:
- 2169-9380
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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