Large-Amplitude Magnetosonic Waves in Muiti-Ion-Species Plasmas

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We have studied, by theory and simulations, propagation of large-amplitude magnetosonic waves and associated particle acceleration in plasmas containing multiple ion species.By using a relativistic particle simulation code, we found that a magnetosonic shock wave can accelerate all the heavy ions to nearly the same speed. This mechanism is different from that of hydrogen acceleration. Thus, as in the solar energetic particles, the high-energy heavy ions have the elemental composition same as that of the background plasma.Magnetosonic pulses are found to be damped in a two-ion-species plasma even if their amplitudes are small and their propagation angles are perpendicular to a magnetic field. This occurs in both the low- and high-frequency modes. This could be an important energy dissipation mechanism in collisionless plasmas such as solar corona.We studied interactions of nonthermal energetic ions with magnetosonic shock waves. Simulations show that some energetic ions can be further accelerated by a shock wave. This result suggests that some ions can be accelerated many times by many different. magnetosonic pulses ; they could therefore obtain quite high energies.We found that ultra-relativistic electrons can be produced in a large-amplitude oblique shock wave. Lorentz factors with gamma > 100 have been observed in our simulations.Large-amplitude magnetosonic waves with relativistic propagation speeds were studied. We theoretically obtained magnetic and electric field strengths as a function of the propagation speed and then analyzed ion motions in such shock waves.