  We consider Cerenkov radiation which must arise when randomly oriented
straight cosmic (super)strings move with relativistic velocities without
intercommutation. String interactions via dilaton, two-form and gravity
(gravity being the dominant force in the ultra-relativistic regime) leads to
formation of superluminal sources which generate Cerenkov radiation of dilatons
and axions. Though the effect is of the second order in the couplings of
strings to these fields, its total efficiency is increased by high dependence
of the radiation rate on the Lorentz-factor of the collision.
