  We report a detailed examination of the "red asymmetry" of H-alpha emission
line seen during the 2001 April 10 solar flare by using a narrowband
filtergram. We investigated the temporal evolution and the spatial distribution
of the red asymmetry by using the H-alpha data taken with the 60cm Domeless
Solar Telescope at Hida Observatory, Kyoto University. We confirmed that the
red asymmetry clearly appeared all over the flare ribbons, and the strong red
asymmetry is located on the outer narrow edges of the flare ribbons, with the
width of about 1.5" - 3.0" (1000 - 2000 km), where the strong energy releases
occur. Moreover, we found that the red asymmetry, which also gives a measure of
the Doppler shift of the H-alpha emission line concentrates on a certain value,
not depending on the intensity of the H-alpha kernels. This implies not only
that the temporal evolutions of the red asymmetry and those of the intensity
are not in synchronous in each flare kernel, but also that the peak asymmetry
(or velocity of the chromospheric condensation) of individual kernel is not a
strong function of their peak intensity.
