Structure and Dynamics of Magnetic Reconnection in a Solar Flare

We report a detailed analysis of the temperature structure of a prototypical flare that occurred on 1992 February 21. In the decay phase of this flare, the outer loops systematically have higher temperatures, reaching the peak (12 MK) far outside the apparent bright X-ray loop where the X-ray intensity is only 2%-5% of the peak. In between the high-temperature ridges, a distinct vertical channel with temperature as low as 8-10 MK is seen at the loop top. In the model presented here, these high-temperature ridges are heated by standing isothermal slow shocks attached to a reconnection point higher in the corona. The cool channel would be formed by conduction cooling as the hot reconnection outflow (12-13 MK) traverses with Mach speed ∼1 (800 km s-1) from the slow-shock region to the loop top. The reconnection point is located 8-18 x 104 km above the apparent top of the flare loop (6 x 104 km), and the inflow speed is estimated to be ∼56 km s-1 (Alfvén Mach number ∼0.07). The bright soft X-ray loops are the reconnected flux tubes subsequently filled with evaporated plasma.