Title: Flare Ribbon Expansion and Energy Release Rate
 
Author_list: Asai, A., Yokoyama, T., Shimojo, M., Masuda, S., Kurokawa,
H., Shibata, K.
  
Abstract: We report a detailed examination about the relationship
between the evolution of the H-alpha flare ribbons and the released
magnetic energy during an X2.3 solar flare which occurred on 2001 April
10.  We examined the evolution of flare ribbons by using the H-alpha
images obtained with the Sartorius telescope at Kwasan Observatory,
Kyoto University.  Based on the magnetic reconnection model, we
calculated quantitatively the released energy was by using the
photospheric magnetic field strengths obtained with SOHO/MDI and
separation speeds of the fronts of the H-alpha flare ribbons.