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Article: On the Origin of Perpendicular Ion Anisotropy Inside Dipolarizing Flux Bundles

TitleOn the Origin of Perpendicular Ion Anisotropy Inside Dipolarizing Flux Bundles
Authors
Keywordsbetatron acceleration
dipolarization front
dipolarizing flux bundle
ion anisotropy
multiple reflection
Issue Date2019
Citation
Journal of Geophysical Research: Space Physics, 2019, v. 124, n. 6, p. 4009-4021 How to Cite?
AbstractPerpendicular anisotropy of suprathermal ions, observed inside some of the dipolarizing flux bundles (DFBs) in the magnetotail plasma sheet, have been attributed to successive, betatron-type accelerations during the DFB entry of ambient ions. It has been unclear, however, where and how these ions enter the DFBs. The proposed locations include the DFB flanks where cross-tail drifting ions are picked up, and the DFB leading edge with sharp magnetic field gradient (the dipolarization front, DF). Here we examine the latter scenario, based on a simplistic, test particle approach, to predict the preferred conditions for the appearance of the DFB ion anisotropy. Our model predicts that the ion anisotropy would be stronger at locations closer to the neutral sheet and would appear preferentially in the DFB dawnside and central sectors rather than the duskside sector. We also predict that the ion anisotropy would more likely be observed in DFBs with higher propagation speeds. These properties can be understood in our model by the dawnward drift of ions during their DF penetration (attributed to the large magnetic gradient). To examine these predictions, we carry out a statistical survey based on observations from the THEMIS (Time History of Events and Macroscale Interactions during Substorms) mission, to show a clear dependence of the ion anisotropy on spacecraft location and the DFB propagation speed. These findings, therefore, are consistent with the scenario that the perpendicular ion anisotropy originates from the ion acceleration and penetration across sharp DFs.
Persistent Identifierhttp://hdl.handle.net/10722/334594
ISSN
2023 Impact Factor: 2.6
2023 SCImago Journal Rankings: 0.845
ISI Accession Number ID

 

DC FieldValueLanguage
dc.contributor.authorZhou, Xu Zhi-
dc.contributor.authorXu, Yan-
dc.contributor.authorRunov, Andrei-
dc.contributor.authorLiu, Jiang-
dc.contributor.authorArtemyev, Anton V.-
dc.contributor.authorAngelopoulos, Vassilis-
dc.contributor.authorBirn, Joachim-
dc.contributor.authorYao, Zhonghua-
dc.contributor.authorPan, Dong Xiao-
dc.contributor.authorZong, Qiu Gang-
dc.date.accessioned2023-10-20T06:49:15Z-
dc.date.available2023-10-20T06:49:15Z-
dc.date.issued2019-
dc.identifier.citationJournal of Geophysical Research: Space Physics, 2019, v. 124, n. 6, p. 4009-4021-
dc.identifier.issn2169-9380-
dc.identifier.urihttp://hdl.handle.net/10722/334594-
dc.description.abstractPerpendicular anisotropy of suprathermal ions, observed inside some of the dipolarizing flux bundles (DFBs) in the magnetotail plasma sheet, have been attributed to successive, betatron-type accelerations during the DFB entry of ambient ions. It has been unclear, however, where and how these ions enter the DFBs. The proposed locations include the DFB flanks where cross-tail drifting ions are picked up, and the DFB leading edge with sharp magnetic field gradient (the dipolarization front, DF). Here we examine the latter scenario, based on a simplistic, test particle approach, to predict the preferred conditions for the appearance of the DFB ion anisotropy. Our model predicts that the ion anisotropy would be stronger at locations closer to the neutral sheet and would appear preferentially in the DFB dawnside and central sectors rather than the duskside sector. We also predict that the ion anisotropy would more likely be observed in DFBs with higher propagation speeds. These properties can be understood in our model by the dawnward drift of ions during their DF penetration (attributed to the large magnetic gradient). To examine these predictions, we carry out a statistical survey based on observations from the THEMIS (Time History of Events and Macroscale Interactions during Substorms) mission, to show a clear dependence of the ion anisotropy on spacecraft location and the DFB propagation speed. These findings, therefore, are consistent with the scenario that the perpendicular ion anisotropy originates from the ion acceleration and penetration across sharp DFs.-
dc.languageeng-
dc.relation.ispartofJournal of Geophysical Research: Space Physics-
dc.subjectbetatron acceleration-
dc.subjectdipolarization front-
dc.subjectdipolarizing flux bundle-
dc.subjection anisotropy-
dc.subjectmultiple reflection-
dc.titleOn the Origin of Perpendicular Ion Anisotropy Inside Dipolarizing Flux Bundles-
dc.typeArticle-
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1029/2019JA026519-
dc.identifier.scopuseid_2-s2.0-85066986808-
dc.identifier.volume124-
dc.identifier.issue6-
dc.identifier.spage4009-
dc.identifier.epage4021-
dc.identifier.eissn2169-9402-
dc.identifier.isiWOS:000477723100011-

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