Flare Ribbon Expansion and Energy Release

A. Asai (Kyoto Univ.), T. Yokoyama, M. Shimojo, S. Masuda, H. Kurokawa,
	and K. Shibata

  We examined the relationship between the evolution of the H-alpha
flare ribbons and the released magnetic energy in a solar flare which
occurred on 2001 April 10.  Based on the magnetic reconnection model,
the released energy was quantitatively calculated by using the
photospheric magnetic field strengths and separation speeds of the
fronts of the H-alpha flare ribbons.  We estimated the magnetic energy
released during the flare.  The estimated energy release rates in the
H-alpha kernels associated with the hard X-ray sources are locally
large enough to explain the difference between the spatial
distribution of the H-alpha kernels and the hard X-ray sources.
  Then, we identified the conjugate footpoints of each H-alpha kernel
in both flare ribbons by using crosscorrelation functions of the light
curves.  We found that the highly-correlated pairs of H-alpha kernels
were connected by flare loops seen in extreme ultraviolet images.
Investigating such fine structures inside the flare ribbons, we have
been able to follow the history of energy release and perhaps acquire
key information about particle acceleration.