Parameter dependence of pressure-gradient driven plasmoid formation and its ejection from host magnetic island

The dynamics of a pressure-gradient driven plasmoid (p-plasmoid) are investigated using numerical simulations based on a two-fluid model of magnetized plasmas, including ion and electron diamagnetic effects. The p-plasmoid is devoid of a pressure gradient confined by locally concentric magnetic flux and is generated in a host magnetic island produced by a resistive interchange mode driven by the pressure gradient across a neutral magnetic sheet. Through a series of parameter scans, the p-plasmoid formation and its ejection from the host island are found to be controlled by the electron diamagnetic velocity inside the island. The ion skin depth and plasma resistivity scans show that the p-plasmoid is formed and ejected from the island for low-density and low-temperature plasmas. By a magnetic configuration scan, a higher magnetic shear and a able averaged curvature is found to be effective in avoiding the formation and ejection of the p-plasmoid. It is also found that a strong monopolar vortex flow is induced in the p-plasmoid, which can be in the clockwise and counter-clockwise directions, contributing to the sustainment of the p-plasmoid.