Evolution of dipolarization in the near-Earth current sheet induced by Earthward rapid flux transport
2009 (English)In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 27, no 4, 1743-1754 p.Article in journal (Refereed) Published
We report on the evolution of dipolarization and associated disturbances of the near-Earth current sheet during a substorm on 27 October 2007, based upon Cluster multi-point, multi-scale observations of the night-side plasma sheet at X similar to - 10R(E). Three dipolarization events were observed accompanied by activations on ground magnetograms at 09: 07, 09: 14, and 09: 22 UT. We found that all these events consist of two types of dipolarization signatures: (1) Earthward moving dipolarization pulse, which is accompanied by enhanced rapid Earthward flux transport and is followed by current sheet disturbances with decrease in B-Z and enhanced local current density, and subsequent (2) increase in B-Z toward a stable level, which is more prominent at Earthward side and evolving tailward. During the 09: 07 event, when Cluster was located in a thin current sheet, the dipolarization and fast Earthward flows were also accompanied by further thinning of the current sheet down to a half-thickness of about 1000 km and oscillation in a kink-like mode with a period of similar to 15 s and propagating duskward. Probable cause of this "flapping current sheet" is shown to be the Earthward high-speed flow. The oscillation ceased as the flow decreased and the field configuration became more dipolar. The later rapid flux transport events at 09: 14 and 09: 22 UT took place when the field configuration was initially more dipolar and were also associated with B-Z disturbance and local current density enhancement, but to a lesser degree. Hence, current sheet disturbances induced by initial dipolarization pulses could differ, depending on the configuration of the current sheet.
Place, publisher, year, edition, pages
2009. Vol. 27, no 4, 1743-1754 p.
Magnetospheric physics, Plasma convection, Plasma sheet, Storms and substorms
IdentifiersURN: urn:nbn:se:uu:diva-148698DOI: 10.5194/angeo-27-1743-2009ISI: 000265603100036OAI: oai:DiVA.org:uu-148698DiVA: diva2:402852