The positions and lengths dong the Solar limb for several eruptive pro
minences and the corresponding coronal transients are compared, Transi
ent loops are by a factor of 2 to 3 wider than prominences in the dire
ction of position angle and are located symmetrically with respect to
prominences, A model of transient formation is suggested that consider
s the transients to form as a result of drift motions of coronal plasm
a in the electromagnetic field of the rising electric current of the f
ilament. The model describes the formation of a cavity around the fila
ment and of the outer loop of the transient, which moves at a speed th
at exceeds the speed of the rising prominence.