  We show that an electronic beam passing through the collisionless plasma of
the "cold" ions and the "hot" Boltzmann electrons can give rise to the
propagation of the supersonic ion-acoustic rarefaction shock waves. These waves
are analogous to those predicted by Zeldovich [5] in gasodynamics and
complementary to the ion-acoustic compression shock waves in collisionless
plasma described by Sagdeev [3].
