An Explosive Scaling Law for Nonlinear Magnetic Reconnection and Its Insensitivity to Microscopic Scales’0

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Abstract

The nonlinear phase of magnetic reconnection is investigated by numerically solving a gyrofluid model. The scaling law for the explosive reconnection rate, which has been recently derived for an ideal two-fluid model [Hi-rota et al., Phys. Plasmas 22, 052114 (2015)], is found to consistently hold when either the ion-sound gyroradius ρS or the ion gyroradius ρi is comparable to the electron skin depth de, even in the presence of finite resistivity η. In this explosive phase, a local X-shaped current layer is spontaneously generated, in which the reconnection speed is closely related to the macroscopic shape of the layer and is almost independent of the layer width. The reconnection speed is therefore insensitive to the size of the microscopic scales, ρS, ρi, de and n. On the other hand, in the cold plasma limit, where ρS = ρi = 0, the intermittent acceleration of the reconnection speed is caused by the plasmoid instability. This also seems to be explosive on average, but the rate always falls below the explosive scaling law. The reconnection time extrapolated from this scaling law is shown to be fast enough to explain the time scale ofsolar flares.

Original languageEnglish
Pages (from-to)1-8
Number of pages8
JournalPlasma and Fusion Research
Volume12
DOIs
Publication statusPublished - 2017

Keywords

  • explosive instability
  • gyrofluid model
  • magnetic reconnection
  • plasmoid instability
  • solar flare

ASJC Scopus subject areas

  • Condensed Matter Physics

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