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Scale size and life time of energy conversion regions observed by Cluster in the plasma sheet
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
Institute for Space Sciences, Bucharest, Romania.
Swedish Institute of Space Physics, Uppsala, Sweden.
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2009 (Engelska)Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 27, nr 11, s. 4147-4155Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

In this article, and in a companion paper by Hamrin et al. (2009) [Occurrence and location of concentrated load and generator regions observed by Cluster in the plasma sheet], we investigate localized energy conversion regions (ECRs) in Earth's plasma sheet. From more than 80 Cluster plasma sheet crossings (660 h data) at the altitude of about 15–20 RE in the summer and fall of 2001, we have identified 116 Concentrated Load Regions (CLRs) and 35 Concentrated Generator Regions (CGRs). By examining variations in the power density, E·J, where E is the electric field and J is the current density obtained by Cluster, we have estimated typical values of the scale size and life time of the CLRs and the CGRs. We find that a majority of the observed ECRs are rather stationary in space, but varying in time. Assuming that the ECRs are cylindrically shaped and equal in size, we conclude that the typical scale size of the ECRs is 2 RE≲ΔSECR≲5 RE. The ECRs hence occupy a significant portion of the mid altitude plasma sheet. Moreover, the CLRs appear to be somewhat larger than the CGRs. The life time of the ECRs are of the order of 1–10 min, consistent with the large scale magnetotail MHD simulations of Birn and Hesse (2005). The life time of the CGRs is somewhat shorter than for the CLRs. On time scales of 1–10 min, we believe that ECRs rise and vanish in significant regions of the plasma sheet, possibly oscillating between load and generator character. It is probable that at least some of the observed ECRs oscillate energy back and forth in the plasma sheet instead of channeling it to the ionosphere.

Ort, förlag, år, upplaga, sidor
2009. Vol. 27, nr 11, s. 4147-4155
Nationell ämneskategori
Fusion, plasma och rymdfysik
Forskningsämne
rymd- och plasmafysik
Identifikatorer
URN: urn:nbn:se:umu:diva-27012DOI: 10.5194/angeo-27-4147-2009OAI: oai:DiVA.org:umu-27012DiVA, id: diva2:275612
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This work is distributed under the Creative Commons Attribution 3.0 License

Tillgänglig från: 2009-11-06 Skapad: 2009-11-06 Senast uppdaterad: 2018-06-08Bibliografiskt granskad

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Förlagets fulltexthttp://www.ann-geophys.net/27/4147/2009/angeo-27-4147-2009.pdf

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Hamrin, MariaNorqvist, Patrik

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