This was not a particulary strong flare, but under special observation in H-alpha. The BBSO (Haimin) made a particulary high resolution H-alpha observations. Originally meant to study the elementary bursts. The elementary bursts is like a quantum of the energy release process. How small & how fast are unknown, therefore  requires as fastest and most detail images as possible.  We then adapted the data to other purpose, as typical in solar study: I.e. test the reconnection theory (usually known as Kopp&Pneuman model for erupting filament) and particle acceleration in DC electric fields. (a) H-alpha and radio contours, (b) magnetogram, © HXR/yohkoh., Conclusion. In favor of the DC field acceleration model. (The electric field is strenght was kind of too high, compared with previous speculation—just a result of increased time/spatial resolution)