On the effect of localized plasma flow on the plasmoid instability in a compressible plasma

In the two-dimensional framework of compressible resistive MHD, we examine the effect of localized plasma flow on the evolution of plasmoids magnetic islands induced during magnetic reconnection with different values of velocity amplitude, ranging from sub-Alfvénic to super-Alfvénic levels. To better understand the influence of localized flow on plasmoid formation and the nonlinear evolution of the current sheet (known as plasmoid instability), we considered a wide range of velocity amplitudes and scale lengths of localized flow. The simulation results show that, by increasing the velocity amplitude from sub-Alfvénic to super-Alfvénic within a scale length smaller than the current sheet thickness, plasmoid instability (PI) is suppressed, and the initial structure of the current sheet is preserved. The growth rate of PI decreases as the localized flow thickness increases, indicating that the scale length of localized flow is a significant parameter in the magnetic reconnection process. The presence of localized plasma flow in the current layer causes a displacement of the initial magnetic reconnection site (primary X-point). Due to multiple reconnections in sub-Alfvénic flows, the initial X-point movement velocity increases in the direction of the localized flow, while in super-Alfvénic flows, the movement velocity of the initial X-point decreases, as magnetic reconnection does not occur. Thus, the growth rate of PI decreases with increasing localized flow velocity amplitude.