丝状等离子体爆发和电子的加热与加速
Filamentary plasma eruptions and the heating and acceleration of electrons
摘要：
我们提出了测试粒子模拟的电子在非线性MHD模拟的I型边缘局域模（ELM），探讨了一个喷发的等离子体灯丝的动力学水平的影响。电子被适度加热和加速在一个快速的时间尺度上的顺序为0.5毫秒的火山喷发。一个明显的非热尾形成的动能的分布是幂律的形状，并达到90千电子伏的一些粒子。加速度是专门观察到的方向平行于磁场，即具有明显的偏好，在逆流方向，我们表明，平行的电场是所观察到的加速度的原因。大多数从系统中逃逸的粒子在其逃逸过程中的某个时间离开偏滤器外腿中的一条明显的走向线。处于能量分布尾部的逃逸高能电子不受碰撞的影响，表现出逃逸电子的特征。均方位移表明，在能量空间中的运输显然是超扩散的，并解释作为一个随机行走的加速过程，我们发现，能量增量的分布呈现指数尾，在能量空间中的运输是同样重要的对流（系统）和扩散（随机）的性质。通过分析MHD模拟本身，结果表明，在边缘区域的平行电场的直方图呈现幂律形状，这种明显的非高斯统计最终是我们在能量空间中发现的粒子输运的适度异常现象的原因之一。
英文摘要：
We present test-particle simulations of electrons during a nonlinear MHD simulation of a type-I edge localized mode (ELM) to explore the effect of an eruptive plasma filament on the kinetic level. The electrons are moderately heated and accelerated during the filamentary eruption on a fast time scale of the order of 0.5 ms. A clearly non-thermal tail is formed in the distribution of the kinetic energy that is of power-law shape and reaches 90 keV for some particles. The acceleration is exclusively observed in the direction parallel to the magnetic field, i.e. with a clear preference in counter-current direction, and we show that the parallel electric field is the cause of the observed acceleration. Most particles that escape from the system leave at one distinct strike-line in the outer divertor leg at some time during their energization. The escaping high energy electrons in the tail of the energy distribution are not affected by collisions, they thus show characteristics of runaway electrons. The mean square displacement indicates that transport in energy space clearly is super-diffusive, and interpreting the acceleration process as a random walk, we find that the distributions of energy-increments exhibit exponential tails, and transport in energy space is equally important of convective (systematic) and diffusive (stochastic) nature. By analyzing the MHD simulations per se, it turns out that the histograms of the parallel electric field in the edge region exhibit power-law shapes, and this clearly non-Gaussian statistics is ultimately one of the reasons for the moderately anomalous phenomena of particle transport that we find in energy space.
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