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The orientation and current density of the magnetotail current sheet: A statistical study of the effect of geomagnetic conditions

Davey, EA; Lester, M; Milan, SE; Fear, RC; Forsyth, C; (2012) The orientation and current density of the magnetotail current sheet: A statistical study of the effect of geomagnetic conditions. JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS , 117 , Article A07217. 10.1029/2012JA017715. Green open access

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Abstract

We examine the orientation and current density of the current sheet during current sheet crossings from Cluster's 2001–2007 tail seasons. The curlometer technique is used to estimate the current density and is combined with Minimum Variance Analysis (MVA) to calculate the direction of the current sheet normal. The SYM-H and AE indices at the time of each crossing are employed to assess how the tilt angle (the angle the normal makes with the Z axis in the GSM YZ plane) and current density depend on geomagnetic conditions. Our results indicate a larger current sheet tilt in the YZ plane during intervals of stronger and/or more prolonged substorm activity, as indicated by the AE index. There is also evidence that when the ring current is enhanced during magnetic storms, the current sheet is less tilted even though the AE index is also disturbed. In addition larger current densities are seen during times of both magnetic storms and substorms, compared to crossings during only substorms and a quiet ring current. We conclude that increased substorm activity disrupts the current sheet structure resulting in greater motion of the current sheet (as found by Davey et al. (2012)) and a greater local tilt to the current sheet. We propose that the increased open flux in the tail during magnetic storms stabilizes the current sheet such that the tilt angle of the current sheet is reduced. The increased amount of open flux during magnetic storms also results in larger current densities within the current sheet.

Type: Article
Title: The orientation and current density of the magnetotail current sheet: A statistical study of the effect of geomagnetic conditions
Open access status: An open access version is available from UCL Discovery
DOI: 10.1029/2012JA017715
Publisher version: http://dx.doi.org/10.1029/2012JA017715
Language: English
Additional information: © 2012 American Geophysical Union
Keywords: Active perturbation experiments, Magnetic storms and substorms, Magnetospheric physics, Magnetotail
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/1346562
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