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

我们从理论和模拟两方面研究了大振幅磁声波在多离子等离子体中的传播和粒子加速，利用相对论粒子模拟程序，我们发现磁声冲击波可以将所有重离子加速到几乎相同的速度。这一机制不同于氢加速的机制。因此，就像在太阳高能粒子中一样，高能重离子具有与背景等离子体相同的元素组成。人们发现，在双离子物种的等离子体中，即使磁声脉冲的幅度很小，并且其传播角与磁场垂直，也会受到抑制。这在低频和高频模式下都会发生。这可能是日冕等无碰撞等离子体中一种重要的能量耗散机制。我们研究了非热高能离子与磁声激波的相互作用。模拟结果表明，一些高能离子可以被激波进一步加速。这一结果表明，一些离子可以通过许多不同的方式被多次加速。磁声脉冲，因此它们可以获得相当高的能量。我们发现，在大振幅斜激波中可以产生超相对论电子。在我们的模拟中观测到了具有伽马&GT；100的洛伦兹因子。研究了具有相对论传播速度的大振幅磁声波。我们从理论上得到了磁场和电场强度作为传播速度的函数，然后分析了离子在这种激波中的运动。

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.