High‐energy tail formation by a monochromatic wave in the magnetized plasma

High‐energy tail formations due to the monochromatic wave in a magnetized plasma are studied numerically and analytically. By calculating the phase space trajectories of 10 000 particles, initially Maxwell‐velocity‐distributed, in the presence of a uniform magnetic field and a sinusoidal wave traveling closely in the perpendicular direction with the frequency of cyclotron harmonics, some properties of particle acceleration are clarified. The acceleration mechanism can be described by a modification of trapping theory and two types of stochastic acceleration. The behavior of the high‐energy tail formation depends on the magnitude of ω/Ω. For small ω/Ω (ω/Ω≲10), the cyclotron harmonics resonance is very important. The ratio of the perpendicular wavelength to the average Larmor radius and the wave amplitude play an important role in determining the ratio of tail to the bulk portion.