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| Titel |
The ideal tearing mode: 2D MHD simulations in the linear and nonlinear regimes |
| VerfasserIn |
Simone Landi, Luca Del Zanna, Fulvia Pucci, Marco Velli, Emanuele Papini |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250104072
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| Publikation (Nr.) |
 EGU/EGU2015-3494.pdf |
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| Zusammenfassung |
| We present compressible, resistive MHD numerical simulations of the linear and nonlinear
evolution of the tearing instability, for both Harris sheet and force-free initial equilibrium
configurations. We analyze the behavior of a current sheet with aspect ratio S1/3, where S is
the Lundquist number. This scaling has been recently recognized to be the threshold for fast
reconnection occurring on the ideal Alfvenic timescale, with a maximum growth rate that
becomes asymptotically independent on S. Our simulations clearly confirm that the tearing
instability maximum growth rate and the full dispersion relation are exactly those predicted
by the linear theory, at least for the values of S explored here. In the nonlinear stage, we
notice the rapid onset and subsequent coalescence of plasmoids, as observed in previous
simulations of the Sweet-Parker reconnection scenario. These findings strongly
support the idea that in a fully dynamic regime, as soon as current sheets develop and
reach the critical threshold in their aspect ratio of S1/3 (occurring well before the
Sweet-Parker configuration is able to form), the tearing mode is able to trigger
fast reconnection and plasmoids formation on Alfvenic timescales, as required to
explain the violent flare activity often observed in solar and astrophysical plasmas. |
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