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Current reduction in a pseudo-breakup event: THEMIS observations

Yao, ZH; Pu, ZY; Owen, CJ; Fu, SY; Chu, XN; Liu, J; Angelopoulos, V; ... Du, AM; + view all (2014) Current reduction in a pseudo-breakup event: THEMIS observations. Journal of Geophysical Research: Space Physics , 119 (10) pp. 8178-8187. 10.1002/2014JA020186. Green open access

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Pseudo-breakup events are thought to be generated by the same physical processes as substorms. This paper reports on the cross-tail current reduction in an isolated pseudo-breakup observed by three of the THEMIS probes (THEMIS A (THA), THEMIS D (THD), and THEMIS E (THE)) on 22 March 2010. During this pseudo-breakup, several localized auroral intensifications were seen by ground-based observatories. Using the unique spatial configuration of the three THEMIS probes, we have estimated the inertial and diamagnetic currents in the near-Earth plasma sheet associated with flow braking and diversion. We found the diamagnetic current to be the major contributor to the current reduction in this pseudo-breakup event. During flow braking, the plasma pressure was reinforced, and a weak electrojet and an auroral intensification appeared. After flow braking/diversion, the electrojet was enhanced, and a new auroral intensification was seen. The peak current intensity of the electrojet estimated from ground-based magnetometers, ~0.7 × 105 A, was about 1 order of magnitude lower than that in a typical substorm. We suggest that this pseudo-breakup event involved two dynamical processes: a current-reduction associated with plasma compression ahead of the earthward flow and a current-disruption related to the flow braking/diversion. Both processes are closely connected to the fundamental interaction between fast flows, the near-Earth ambient plasma, and the magnetic field.

Type: Article
Title: Current reduction in a pseudo-breakup event: THEMIS observations
Open access status: An open access version is available from UCL Discovery
DOI: 10.1002/2014JA020186
Publisher version: http://dx.doi.org/10.1002/2014JA020186
Language: English
Additional information: Copyright © 2014 The Authors. This is an open access article under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Keywords: science & technology, physical sciences, astronomy & astrophysics, field-aligned currents, fast flow, current disruption, substorm, pressure gradient, dipolarization front, substorm current wedge, current disruption, mhd simulations, current sheet, growth-phase, flow bursts, plasma-flow, braking, tail, dipolarization
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/1449216
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