Slow and fast magnetic reconnection I. Role of radiative cooling

Abstract

Newmodelofamagneticallynon-neutralreconnect- ing current sheet (RCS) in the solar corona is developed to in- vestigate different structures of the RCS and different regimes of reconnection corresponding to these structures. In this pa- per (Paper 1) we formulate the mathematical problem and con- sider mainly the solutions that demonstrate an influence of the radiative cooling on the RCS structure and reconnection rate. The solution for low temperatures (T 10 4 K) of plasma in the RCS, when heat conduction is not important, shows that the radiative losses of energy make the current sheet be thin- ner, denser, and colder; the velocity of plasma outflows from it slows down. The transition from the slow regime of reconnec- tion(withthemagneticeldcongurationofO-typeinacentral region of the RCS) to the fast one (with the conguration of X- type)isrealizedatlargerratesofreconnectionascomparedwith the case where radiation is not taken into account. This result makes more probable the formation of solar prominences via slow magnetic reconnection in the RCS with magnetic island in the central region of current sheet. The transition from slow reconnection to fast one presumably means destabilization of a quiescent prominence and triggering a flare.