Abstract
Relativistic particle dynamics is studied analytically and numerically in the electrostatic wave propagating obliquely to the uniform static magnetic field. The criterion is obtained that there exist the particles which keep trapped if the ratio of the field strength of the electrostatic wave to that of the static magnetic field is greater than the critical value which is a function of the propagation angle and the phase velocity of the electrostatic wave. The trapped particles can be accelerated unlimitedly if the propagation angle is larger than the angle which is determined from the phase velocity. The maximum acceleration gradient is also obtained as a function of the field strength, the phase velocity and the propagation angle of the wave.
