The fluorescence of iron lines in solar flares

The iron-fluorescence mechanism is investigated using a semiempirical model of chromospheric flares. The radiation field of H Ca II + H-epsilon is considered in the present non-LTE calculations for the iron atom model. It is shown that the observed fluorescent strengthening in the range from 4063 to 4132 of Fe I may be obtained if additional broadening of H Ca II + H-epsilon or differential motions in flares is assumed. It is concluded that the most probable cause of the strengthening in the range from 4063 to 4132 of Fe I is the H-epsilon line emission in flare gas moving toward the center of the sun. The velocity gradient of two observed flares is estimated using a 1-point flare model.