Interaction between low energy proton ring-beam and plasma with one-dimentional hybrid simulations

In this paper, the interaction between the low energy proton ring-beam with an initial velocity perpendicular to the background magnetic field, and the background plasma is studied by one-dimensional (1D) hybrid simulations. In the initial stage, the excited plasma waves experience a fast growth exponentially, which is consistent with the linear theory. After that, three non-linear stages, including the saturation process, the fast damping process and the relatively stable stage, follow in sequence. In the linear stage, the mode-resonance damps with the pitch angle scattering of the injected protons, and the plasma oscillation reaches the peak quickly. The continuing pitch angle scattering makes the velocity distributions of the proton beam and the background ions uniformly distributed. Meanwhile, the initially excited right-handed resonant instability decreased, with only the Alfven waves left in the stable stage. The results also show that the effective heating of the background plasma is achieved after the linear stage, instead from the very beginning of the injection of the protons. This demonstrates that the excited plasma waves lead to the energy transferring from the injected proton beams to the background plasma.