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| Titel |
Reconnection in substorms and solar flares: analogies and differences |
| VerfasserIn |
J. Birn, M. Hesse |
| 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. 3 ; Nr. 27, no. 3 (2009-03-04), S.1067-1078 |
| Datensatznummer |
250016440
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| Publikation (Nr.) |
 copernicus.org/angeo-27-1067-2009.pdf |
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| Zusammenfassung |
| Magnetic reconnection is the crucial process in the release of magnetic
energy associated with magnetospheric substorms and with solar flares. On the
basis of three-dimensional resistive MHD simulations we investigate
similarities and differences between the two scenarios. We address in
particular mechanisms that lead to the onset of reconnection and energy
release, transport, and conversion mechanisms. Analogous processes might
exist in the motion of field line footpoints on the sun and in magnetic flux
addition to the magnetotail. In both cases such processes might lead to a
loss of neighboring equilibrium, characterized by the formation of a very thin
embedded current sheet, which acts as trigger for reconnection. We find that
Joule (or ohmic) dissipation plays only a minor role in the overall energy
transfer associated with reconnection. The dominant transfer of released
magnetic energy occurs to electromagnetic energy (Poynting) flux and to
thermal energy transport as enthalpy flux. The former dominates in low-beta,
specifically initially force-free current sheets expected for the solar
corona, while the latter dominates in high-beta current sheets, such as the
magnetotail. In both cases the outflow from the reconnection site becomes
bursty, i.e. spatially and temporally localized, yet carrying most of the
outflow energy. Hence an analogy might exist between bursty bulk flows (BBFs)
in the magnetotail and pulses of Poynting flux in solar flares. Further
similarities might exist in the role of collapsing magnetic flux tubes, as a
consequence of reconnection, in the heating and acceleration of charged
particles. |
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