ANGEO Annales Geophysicae ANGEO Ann. Geophys. 1432-0576 Copernicus Publications Göttingen, Germany 10.5194/angeo-28-1813-2010 Geomagnetic activity effects on plasma sheet energy conversion Hamrin M. 1 Norqvist P. 1 Marghitu O. 2 Buchert S. 3 Klecker B. 4 Kistler L. M. 5 Dandouras I. 6 Department of Physics, Umeå University, Umeå, Sweden Institute for Space Sciences, Bucharest, Romania Swedish Institute of Space Physics, Uppsala, Sweden Max-Planck-Institut für extraterrestrische Physik, Garching, Germany Space Science Center, University of New Hampshire, Durham, USA CESR-CNRS, Toulouse, France 01 10 2010 28 10 1813 1825 Copyright: © 2010 M. Hamrin et al. 2010 This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/ This article is available from https://angeo.copernicus.org/articles/28/1813/2010/angeo-28-1813-2010.html The full text article is available as a PDF file from https://angeo.copernicus.org/articles/28/1813/2010/angeo-28-1813-2010.pdf

In this article we use three years (2001, 2002, and 2004) of Cluster plasma sheet data to investigate what happens to localized energy conversion regions (ECRs) in the plasma sheet during times of high magnetospheric activity. By examining variations in the power density, <I><B>E</B></I>&middot;<I><B>J</B></I>, where <I><B>E</B></I> is the electric field and <I><B>J</B></I> is the current density obtained by Cluster, we have studied the influence on Concentrated Load Regions (CLRs) and Concentrated Generator Regions (CGRs) from variations in the geomagnetic disturbance level as expressed by the Kp, the AE, and the Dst indices. We find that the ECR occurrence frequency increases during higher magnetospheric activities, and that the ECRs become stronger. This is true both for CLRs and for CGRs, and the localized energy conversion therefore concerns energy conversion in both directions between the particles and the fields in the plasma sheet. A higher geomagnetic activity hence increases the general level of energy conversion in the plasma sheet. Moreover, we have shown that CLRs live longer during magnetically disturbed times, hence converting more electromagnetic energy. The CGR lifetime, on the other hand, seems to be unaffected by the geomagnetic activity level. The evidence for increased energy conversion during geomagnetically disturbed times is most clear for Kp and for AE, but there are also some indications that energy conversion increases during large negative Dst. This is consistent with the plasma sheet magnetically mapping to the auroral zone, and therefore being more tightly coupled to auroral activities and variations in the AE and Kp indices, than to variations in the ring current region as described by the Dst index.

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