  The energy loss by a test gyratory particle in a cold plasma in the presence
of homogeneous magnetic field is considered. Analytical and numerical results
for the rate of energy loss are presented. This is done for strong and weak
fields (i. e., when the electron cyclotron frequency is either higher, or
smaller than the plasma frequency), and in case, when the test particle
velocity is greater than the electron thermal velocity. It is shown that the
rate of energy loss may be much higher than in the case of motion through
plasma in the absence of magnetic field.
