Current point formation and magnetic reconnection process in nonlinearly destabilized double tearing modes

• Published in: Physics of plasmas 2003-09, Vol.10 (9), p.3512-3520
• Main Authors: Ishii, Y., Azumi, M., Kishimoto, Y.
• Format: Article
• Language: English
• ISSN: 1070-664X; 1089-7674
• DOI: 10.1063/1.1594187

Magnetic reconnection process triggered by the nonlinearly destabilized double tearing mode (DTM) is studied in detail. A localized plasma current, which is referred as a current point, is formed at the X -type reconnection region of the outer magnetic island in the nonlinear growth phase of DTM [Phys. Rev. Lett. 89, 205002 (2002)]. Magnetic reconnection process with a current point shows new features different from those with the well-known Sweet–Parker type current sheet. In contrast to the latter one, the inverse aspect ratio of the plasma current at the reconnection region of the outer magnetic island, δ/Δ, increases in the Rutherford type phase and decreases after the nonlinear destabilization of DTM is triggered. The weak dependence of the temporal growth rate on the plasma resistivity in the explosive growth phase is due to this unique temporal evolution of the spatial structure of a current point. The simulations in toroidal geometry show that a current point with coherent character is also formed even in the stochastic magnetic field resultant from overlapping magnetic islands with different helicity.