Production of Ultrarelativistic Particles by Large-Amplitude Plasma Waves

我们用理论和计算机模拟研究了“大振幅等离子体波产生超相对论性粒子”。我们的工作可以概括如下。1)利用一维（一个空间坐标和三个速度分量）、相对论、电磁学、粒子模拟程序，研究了电子-正电子-离子等离子体中的波传播和粒子加速。我们已经发现，斜向外磁场传播的磁声激波可以将一些正电子加速到超相对论能量。同时，我们提出了这种加速机制的理论。在模拟中，观察到正电子的洛伦兹因子为γ ~ 1000。2)从理论上和数值上研究了斜激波对非热快速离子的加速作用。通过实验粒子模拟，证明了一些快速离子可以从γ ~ 1加速到γ ~ 100。还研究了能量和动量分布函数的演化。在动量空间中，这些快速离子沿双曲线扩散。3)从理论上详细研究了电子对超相对论能量的加速。我们得到了激波所加速的最大能量的一个简单表达式。理论与仿真结果吻合较好。4)采用三维静电粒子模拟程序研究了热平衡等离子体中的离子伯恩斯坦波。发现当等离子体中含有多种离子时，这些电场的自相关函数会受到阻尼。5)结合这些研究，我们从理论上研究了线性和非线性磁流体动力波的结构和传播。

We have studied "production of ultrarelativistic particles by large-amplitude plasma waves" with theory and computer simulations. Our work may be summarized as follows.1)By using a one-dimension (one space coordinate and three velocity components), relativistic, electromagnetic, particle simulation code, we have studied the wave propagation and particle acceleration in electron-positron-ion plasmas. We have found that a magnetosonic shock wave, propagating obliquely to an external magnetic field can accelerate some positrons to ultrarelativistic energies. Also, we presented a theory for this acceleration mechanism. in the simulations, positrons with their Lorentz factors γ〜1000 have been observed.2)We investigated theoretically and numerically the acceleration of nonthermal, fast ions by an oblique shock wave. With test particle simulations, it has been demonstrated that some fast ions can be accelerated from γ〜1 to γ〜100. The evolution of energy and momentum distribution functions has also been examined. In the momentum space, these fast ions spread along a hyperbola.3)We theoretically investigated the electron acceleration to ultrarelativistic energies in detail. We obtained a simple expression for the maximum energy accelerated by a shock wave. The theory and simulation results were in good agreement.4)A three-dimension, electrostatic particle simulation code was used to study the ion Bernstein waves in a thermal equilibrium plasma. It is found that autocorrelation functions of these electric fields are damped if the plasma contains multiple ion species.5)In connection with these studies, we have theoretically investigated the structure and propagation of linear and nonlinear magnetohydrodynamic waves.