Kinematics of Flare Ribbons during Eruption of Solar Prominences

Flare ribbons formed in solar two-ribbon flares after eruptions of prominences diverge in opposite directions from the polarity inversion line of the photospheric longitudinal magnetic field, sharply slowing down with time and distance from this line. Examples of such events are given, and the kinematics of flare ribbons is demonstrated. A comparison of the position of the ribbons with the distribution of the photospheric magnetic field shows that the separation of the ribbons slows down when they enter a region of a strong longitudinal field. A simple model of prominence eruption illustrates the kinematic features of the motion of the ribbons and the relation to the sources of the coronal magnetic field in the photosphere.