Measurement of the Energy Release Rate and the Reconnection Rate in Solar Flares

By using the method presented by Isobe et al. (2002), the non-dimensionalreconnection rate Vin/Va has been determined for the impulsive phase of threetwo-ribbon flares, where Vin is the velocity of the reconnection inflow and Vais the Alfven velocity. The non-dimensional reconnection rate is important tomake a constraint on the theoretical models of magnetic reconnection. In orderto reduce the uncertainty of the reconnection rate, it is important todetermine the energy release rate of the flares from observational data asaccurately as possible. To this end, we have carried out one dimensionalhydrodynamic simulations of a flare loop and synthesized the count ratedetected by the soft X-ray telescope (SXT) aboard Yohkoh satellite. We foundthat the time derivative of the thermal energy contents in a flare arcadederived from SXT data is smaller than the real energy release rate by a factorof 0.3 - 0.8, depending on the loop length and the energy release rate. Theresult of simulation is presented in the paper and used to calculate thereconnection rate. We found that reconnection rate is 0.047 for the X2.3 flareon 2000 November 24, 0.015 for the M3.7 flare on 2000 July 14, and 0.071 forthe C8.9 flare on 2000 November 16. These values are similar to that derivedfrom the direct observation of the reconnection inflow by Yokoyama et al.(2001), and consistent with the fast reconnection models such as that ofPetschek (1964).Comment: 27 pages, 12 figures. Accepted for publication in Ap