[en] An anomalous loss mechanism of ions and electrons in a mirror machine is investigated. - The experiments were carried out at the Ogra-3 and Ogra-3B devices with low-density plasma (10⁸-10¹⁰cm^-3). Losses of plasma are the result of its radial transport across the magnetic field under the influence of an oscillating electric field with a frequency comparable to the particle drift frequencies. The well determined character of charged-particle motion in the field of the low-frequency wave is destroyed by the changes in the particle energies. The electron energy changes through Coulomb collisions, and that of the ions as a result of cyclotron oscillations. It is shown experimentally that if the low-frequency oscillations are suppressed cyclotron oscillations do not give rise to ion losses under the conditions of the experiment. (author)