Plasma-beta dependence of the fast reconnection mechanism in an initially force-free current sheet

The present paper systematically studies the spontaneous fast reconnection mechanism in an initially force-free current sheet in a wide range of plasma beta (β); in our previous work it was studied for a special case of β = 0.15. In each case, the evolution as well as the resulting structure of the fast reconnection is qualitatively similar to the one that was already reported for the case of β = 0.15. Quantitatively, the fast reconnection evolution becomes more rapid and drastic for the lower plasma beta. For the cases of very low plasma beta (β = 0.01 or 0.02), the plasma temperature is extremely enhanced to the value almost 1/β times larger than its initial value in the resulting fast reconnection jet and large-scale plasmoid regions. Once the fast reconnection mechanism is ignited in a local spot-like region, its basic structure eventually established is sustained almost steadily, giving rise to the plasmoid swelling with time and propagating outwards. Accordingly, the characteristic reconnection regions, where plasma thermodynamic quantities are remarkably enhanced, rapidly expand in all (x, y, and z) directions in Alfven time scales, which may be responsible for the explosive expansion of large flares as well as for the distinct plasma heating observed in the solar corona.