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| Titel |
Reconstruction of a large-scale reconnection exhaust structure in the solar wind |
| VerfasserIn |
W.-L. Teh, B. U. Ö. Sonnerup, Q. Hu, C. J. Farrugia |
| 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 ; 27, no. 2 ; Nr. 27, no. 2 (2009-02-18), S.807-822 |
| Datensatznummer |
250016415
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| Publikation (Nr.) |
 copernicus.org/angeo-27-807-2009.pdf |
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| Zusammenfassung |
| We recover two-dimensional (2-D) magnetic field and flow
field configurations from three spacecraft encounters with a single
large-scale reconnection exhaust structure in the solar wind, using a new
reconstruction method (Sonnerup and Teh, 2008) based on the ideal
single-fluid MHD equations in a steady-state, 2-D geometry. The
reconstruction is performed in the rest frame of the X-line, where the flow
into, and the plasma jetting within, the exhaust region are clearly visible.
The event was first identified by Phan et al. (2006) in the ACE, Cluster,
and Wind data sets; they argued that quasi-steady reconnection persisted for
over 2 h at a long (390 RE) X-line. The reconnection exhaust is
sandwiched between two discontinuities, both of which contain elements of
intermediate- and slow-mode behavior; these elements are co-located rather
than being spatially separated. These composite discontinuities do not
satisfy the coplanarity condition or the standard MHD jump conditions. For
all three spacecraft, the Walén regression line slope was positive
(negative) for the leading (trailing) discontinuity. Our MHD reconstruction
shows that: (1) the X-line orientation was close to the bisector of the
overall magnetic shear angle and exhibited a slow rotating motion toward the
Sun-Earth line; (2) the X-line moved earthward, dawnward, and southward; (3)
the reconnection electric field was small (~0.02 mV/m on average) and
gradually decreased from the first crossing (ACE) to the last (Wind). The
magnetic field and flow field configurations recovered from ACE and Cluster
are similar while those recovered from Wind also include a magnetic island
and an associated vortex. Reconnection persisted for at least 2.4 h
involving inflow into the exhaust region from its two sides. Time-dependence
in the reconnection electric fields seen by ACE and Wind indicates local
temporal variations in the field configuration. In addition to the
reconstruction results, we provide a description and analysis of many
details from the crossings by the spacecraft. |
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