Dynamics of shear flows in magnetic island coalescence problem using Hall-MHD model

Shear flows are an important attributes of many plasma environment including laboratory and astrophysical plasmas. Although the effect of external flow shear on magnetic reconnection in Harris current sheet set-up has been investigated extensively [1], its effect has not been explored in the magnetic island systems. In a recent work using incompressible resistive MHD model [2], with an in-plane shear flow having amplitude ranging from sub-Alfvénic to super-Alfvénic scale, coalescence instability is found to be dominant against the MHD-Kelvin-Helmholtz instability and upstream/downstream magnetic and flow field components follow different scaling laws [3] in-comparison to that of Harris set-up. However, the effect of compressibility which can be expected to be important for shear flow dynamics and Hall physics was not addressed. In this work, using a compressible MHD code MPI-AMRVAC [4], we investigate the role of Hall term on the in-plane/out-of-plane shear flow affected current sheet properties, reconnection parameters and overall island time evolution during the coalescence process. Likewise, as the island system size is known to play a major role in the Hall-dominant reconnection [5], shear flow effects on this is another important aspect that will be addressed in this work.