Cluster observations of an ion‐scale current sheet in the magnetotail under the presence of a guide field

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Zeitschriftentitel:	Journal of Geophysical Research: Space Physics
Personen und Körperschaften:	Nakamura, R., Baumjohann, W., Fujimoto, M., Asano, Y., Runov, A., Owen, C. J., Fazakerley, A. N., Klecker, B., Rème, H., Lucek, E. A., Andre, M., Khotyaintsev, Y.
In:	Journal of Geophysical Research: Space Physics, 113, 2008, A7
Format:	E-Article
Sprache:	Englisch
veröffentlicht:	American Geophysical Union (AGU)
Schlagwörter:	Paleontology Space and Planetary Science Earth and Planetary Sciences (miscellaneous) Atmospheric Science Earth-Surface Processes Geochemistry and Petrology Soil Science Water Science and Technology Ecology Aquatic Science Forestry Oceanography Geophysics

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Zusammenfassung:	<jats:p>We report on Cluster observations of a thin current sheet interval under the presence of a strong ∣<jats:italic>B</jats:italic><jats:sub><jats:italic>Y</jats:italic></jats:sub>∣ during a fast earthward flow interval between 1655 UT and 1703 UT on 17 August 2003. The strong ∣<jats:italic>B</jats:italic><jats:sub><jats:italic>Y</jats:italic></jats:sub>∣ in the tail could be associated with a strong IMF ∣<jats:italic>B</jats:italic><jats:sub><jats:italic>Y</jats:italic></jats:sub>∣, but the large fluctuations in <jats:italic>B</jats:italic><jats:sub><jats:italic>Y</jats:italic></jats:sub>, not seen in the IMF, suggest that a varying reconnection rate causes a varying transport of <jats:italic>B</jats:italic><jats:sub><jats:italic>Y</jats:italic></jats:sub>‐dominated magnetic flux and/or a change in <jats:italic>B</jats:italic><jats:sub><jats:italic>Y</jats:italic></jats:sub> due to the Hall‐current system. During the encounter of the high‐speed flow, an intense current layer was observed around 1655:53 UT with a peak current density of 182 nA/m<jats:sup>2</jats:sup>, the largest current density observed by the Cluster four‐spacecraft magnetic field measurement in the magnetotail. The half width of this current layer was estimated to be ∼290 km, which was comparable to the ion‐inertia length. Its unique signature is that the strong current is mainly field‐aligned current flowing close to the center of the plasma sheet. The event was associated with parallel heating of electrons with asymmetries, which suggests that electrons moving along the field lines can contribute to a strong dawn‐to‐dusk current when the magnetotail current sheet becomes sufficiently thin and active in a strong guide field case.</jats:p>
ISSN:	0148-0227
DOI:	10.1029/2007ja012760