Viscous effects on plasmoid formation from nonlinear resistive tearing growth in a Harris sheet

In this work, the evolution of a highly unstable m = 1 resistive tearing mode, leading to plasmoid formation in a Harris sheet, is studied in the framework of full MHD model using the Non-Ideal Magnetohydrodynamics with Rotation, Open Discussion simulation. Following the initial nonlinear growth of the primary m = 1 island, the X-point develops into a secondary elongated current sheet that eventually breaks into plasmoids. Two distinctive viscous regimes are found for the plasmoid formation and saturation. In the low viscosity regime (i.e. P (r) less than or similar to 1), the plasmoid width increases sharply with viscosity, whereas in the viscosity dominant regime (i.e. P (r) greater than or similar to 1), the plasmoid size gradually decreases with viscosity. Such a finding quantifies the role of viscosity in modulating the plasmoid formation process through its effects on the plasma flow and the reconnection itself.

Automated summary

The evolution of a highly unstable m = 1 resistive tearing mode, leading to plasmoid formation in a Harris sheet, is studied in this work using the Non-Ideal Magnetohydrodynamics with Rotation, Open Discussion simulation. Two distinctive viscous regimes are found for the plasmoid formation and saturation, with the plasmoid width increasing sharply with viscosity in the low viscosity regime and gradually decreasing with viscosity in the viscosity dominant regime. The role of viscosity in modulating the plasmoid formation process through its effects on the plasma flow and reconnection is quantified.