Nonlinear coherent structures of electrostatic ion cyclotron wave induced by a moving obstacle

The excitations of nonlinear electrostatic ion cyclotron waves arising from a steadily moving charged obstacle are investigated in collisionless plasmas. In the weakly nonlinear and dispersive limit, it is shown that the moving obstacle-induced excitations can be described by a forced Ostrovsky-type model equation. The exact analytical solution predicts that the nonlinear equation does have a periodic solution for a specific analytic form of the obstacle. The computational results are noteworthy, which predict the generation of coherent nonlinear structures, such as bipolar, sawtooth, and multi-harmonic, of the electric field at the transcritical speed of the obstacle along with the wave packets. The results agree well with the astrophysical observations in auroral plasmas.