Flare Ribbon Expansion and Energy Release Rate

We report a detailed examination about the relationship between the evolution of the Halpha flare ribbons and the released magnetic energy during an X2.3 solar flare which occurred on 2001 April 10. We successfully evaluated the released energy quantitatively, based on the magnetic reconnection model. We measured the photospheric magnetic field strengths and the separation speeds of the fronts of the Halpha flare ribbon, and estimated the released magnetic energy at the flare by using those values. Then, we compared the estimated energy release rates with the nonthermal behaviors observed in hard X-rays and microwaves. We also estimated the magnetic energy released during the flare. The estimated energy release rates in the Halpha kernels associated with the hard X-ray sources are locally large enough to explain the difference between the spatial distribution of the Halpha kernels and the hard X-ray sources. Furthermore, we reconstructed the peaks in the nonthermal emission by using the estimated energy release rates.