Study of the Flare and Its Velocity Fields Observed on August 17, 1989

Based on the spectral method of ‘multi-cloud model’ ( MCM), the line-of-sight velocity fields of the flare loops observed at Yunnan Observatory with a two dimensional Spectra-Spect rohelio graph (SSHG) in Hβ line on August 17, 1989 are obtained in the present thesis. Under the condition of certain assumpations and a pproximations, the velocity fields of a flare loop are calculated theoretically according to the MHD theory for several different models of material motion within the loop so as to expiore the regularity of material motion in solar flares. Through a compa rison of both velocity fields, theoretieal and observational ones, it is found that there are two possible models for the material motion in this flare loop system: the matter falls down from thetop of the loop or rises from one loop foot to the top then falls down to another foot, both move along with the legin a helical mag netic line.