Downloads: 44

Files in This Item:
File Description SizeFormat 
2015JA021831.pdf7.59 MBAdobe PDFView/Open
Full metadata record
DC FieldValueLanguage
dc.contributor.authorEbihara, Y.
dc.contributor.authorTanaka, T.
dc.contributor.alternative海老原, 祐輔
dc.description.abstractAuroral breakup at the onset of substorm expansion is sometimes preceded by auroral forms known as quiet arcs and N-S arcs. Observations have shown that both the auroral forms tend to move equatorward, and the initial brightening takes place in or near one of the quiet arcs. The auroral forms attract great attention, but generation of auroral forms and their association with the initial brightening are poorly understood. Recent global magnetohydrodynamic simulations are capable of producing upward field-aligned currents (FACs) that resemble the auroral forms in both shape and temporal evolution. Based on the simulation results, we propose the following scenarios: (1) When the convection electric field is weak (northward interplanetary magnetic field (IMF)), the high-pressure region is elongated from the plasma sheet toward higher latitudes and is structured by a coupling between the magnetosphere and the ionosphere (interchange-like instabilities). (2) When the convection electric field is strong (southward IMF), the structured high-pressure region moves equatorward (toward the plasma sheet). Upward currents are generated around it, which can be observed as arcs in the ionosphere. The upward current can be tentatively intensified in the course of the equatorward movement before the formation of a near-Earth neutral line (NENL). (3) The NENL releases magnetic tension and results in the enhancement of plasma pressure at off-equator in the near-Earth region. Sudden formation of the off-equatorial high-pressure region generates the onset current system that manifests initial brightening. Our scenario can explain the observational fact that poleward arcs remained undisturbed at the onset.
dc.publisherBlackwell Publishing Ltd
dc.rightsAn edited version of this paper was published by AGU. Copyright 2016 American Geophysical Union.
dc.subjectgrowth phase
dc.subjectquiet arcs
dc.subjectN‐S arcs
dc.subjectM‐I coupling
dc.titleSubstorm simulation: Quiet and N-S arcs preceding auroral breakup
dc.type.niitypeJournal Article
dc.identifier.jtitleJournal of Geophysical Research A: Space Physics
dc.addressResearch Institute for Sustainable Humanosphere, Kyoto University
dc.addressInternational Center for Space Weather Science and Education, Kyushu University
dc.identifier.kaken15H03732 / 15H05815
Appears in Collections:Journal Articles

Show simple item record

Export to RefWorks

Export Format: 

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.