Nonlinear evolution and collisionless damping of perpendicular magnetosonic waves

One dimensional electromagnetic simulation code based on a three-fluid model is used to study evolution of perpendicular nonlinear magnetosonic waves in a two-ion-species plasma, in which there are low- and high-frequency magnetosonic modes. A small-amplitude solitary wave of the low-frequency mode propagates steadily without changing its profile. When the amplitude of the solitary pulse is rather large, however, steepening occurs, and short-wavelength solitary waves of the high-frequency mode are generated. On the other hand, a solitary wave of the high-frequency mode accelerates heavy ions in the direction parallel to the wave front, which results in the excitation of a longer-wavelength perturbation behind the pulse. The damping due to the energy transfer from the original pulse to the longer-wavelength perturbation occurs even if the plasma is collisionless and the pulse amplitude is small. The damping rate is theoretically obtained, which is in agreement with the simulation results. (author)