| Abstract : | Magnetic reconnection is a fundamental process observed in both astrophysical and fusion device plasmas. In plasmas, the magnetic reconnection takes place at the local magnetic X-type null points, results in a change of global magnetic field topology and convert a large fraction of magnetic field energy in the form of kinetic energy and bulk plasma heating. Hence, any change in the profile of plasma parameters around the reconnection site can potentially change the reconnection process and affects the system globally. Shear flow in the plasma is one of such parameters and its role in the reconnection process (see Ref. 1 and references therein) has been studied extensively in recent years. In the previous studies, the effect of shear flows on the magnetic reconnection has been explored along with tearing mode instability [2] and plasmoid instability [3] in the Harris-type current sheet only.
In the present work, we study the role of shear flow on the magnetic island coalescence using Fadeev’s equilibrium [4] using a 2D viscoresistive Reduced-MHD (2D VR-RMHD) model [1]. Initially imposed Harris type shear flow quickly changes to vorticity patches concentric to the magnetic islands. This plasma circulation inside the islands results into a secondary anti-parallel shear flow on both sides of the reconnecting current sheet. We report new scaling laws of various parameters like reconnection rate, reconnecting current sheet width, upstream magnetic field with respect to shear flow amplitude and shear length scale. We find the suppression of Kelvin-Helmholtz instability in the super-Alfvenic shear flows.
References :
[1] J. Mahapatra et. al., Phys. Plasmas 28, 072103 (2021).
[2] P. A. Cassak, Phys. Plasmas 18, 072106 (2011).
[3] M. Hosseinpour et. al., Phys. Plasmas 25, 102117 (2018).
[4] V. M. Fadeev et. al., Nucl. Fusion 5,202 (1965).
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