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| Titel |
Cluster observations of a transient signature in the magnetotail: implications for the mode of reconnection |
| VerfasserIn |
S. Beyene, C. J. Owen, A. P. Walsh, C. Forsyth, A. N. Fazakerley, S. Kiehas, I. Dandouras, E. Lucek |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 29, no. 11 ; Nr. 29, no. 11 (2011-11-28), S.2131-2146 |
| Datensatznummer |
250017132
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| Publikation (Nr.) |
 copernicus.org/angeo-29-2131-2011.pdf |
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| Zusammenfassung |
| Travelling compression regions (TCRs) are perturbations in the magnetotail
lobe magnetic field caused by structures moving Earthward or tailward within
the plasma sheet. Previous works have suggested that these structures are
created by either time-dependant reconnection occurring at a single X-line,
forming a flux-bulge-type structure, or space-variant reconnection at
multiple X-lines, forming flux-rope-type structures. In this study we
examine an event in which Cluster 2 observed a TCR while the 3 remaining
Cluster spacecraft observed the underlying magnetic structure at a range of
distances from the neutral sheet. The magnetic structure has a velocity of
(99, 154, −31) km s−1 in GSM (|V| = 186 km s−1),
an estimated size of 1.19 RE along the direction of travel
and a size between 1.94 and 2.86 RE in the direction perpendicular to
the current sheet. As the structure passes the spacecraft, Cluster 1 and
Cluster 4 observed a bipolar signature in BZ, plasma-sheet-like plasma
and field-aligned electron flows. Cluster 3 passed closest to the centre of
the structure and observed two separate reductions in the plasma density
(with field-aligned electron flows); these drop-outs in the plasma sheet
were possibly created by the actions of X-lines. The second drop-out in the
plasma sheet also includes a reversal of the ion flow, a signature
consistent with the passage of a reconnecting X-line past the spacecraft.
Between the X-lines, the plasma outflow from the X-lines caused an increase
in pressure which led to a localised expansion of the plasma and also the
observations at Cluster 1 and Cluster 4 and the TCR. Our observations do not
uniquely match either of the flux rope or the flux bulge predictions
although the observation of two plasma sheet drop-outs (interpreted as
X-lines, one active, one dormant) with plasma-sheet-like between them and
only one TCR is a situation expected in multiple X-line reconnection. |
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