论文标题
在分形环境中随机湍流加速
Stochastic Turbulent Acceleration in a fractal environment
论文作者
论文摘要
我们分析了完全发达的湍流等离子体内颗粒的随机加速度。众所周知，在这种环境中，大振幅磁波动和相干结构遵守分形尺度，我们的具体目的是首次研究这些环境的分形对随机加速的影响。我们已经表明，注射的麦克斯韦能分布被加热并在很短的时间内形成高能量尾巴。使用标准参数用于低太阳能电晕，将电子的麦克斯韦分布从最初的100 eV加热到10 keV，高能尾的幂律指数约为-2.3-4.0。高能尾部开始于100 keV，达到10 MEV。幂律尾部的索引取决于系统的大小，并且与现实的系统大小的观察值非常吻合。加热和加速过程非常快（\ sim 2 s）。加速时间如此短的原因是，颗粒被困在分形环境的小部分中，它们的散射均值自由路径会大大减少。小规模活动的存在也很容易从热池中拉出颗粒，因此不需要种子种群。对于高能颗粒而言，空间和能量的均方根位移是超级延伸的。
We analyze the stochastic acceleration of particles inside a fully developed turbulent plasma. It is well known that large-amplitude magnetic fluctuations and coherent structures in such an environment obey a fractal scaling, and our specific aim is to study for the first time the effects of the fractality of these environments on stochastic acceleration. We have shown that an injected Maxwellian energy distribution is heated and forms a high energy tail in a very short time. Using standard parameters for the low solar corona, the injected Maxwellian distribution of electrons gets heated from the initial 100 eV to 10 KeV, and the power-law index of the high energy tail is about -2.3-4.0. The high energy tail starts around 100 keV, and reaches 10 MeV. The index of the power-law tail depends on the system size, and it is in good agreement with observed values for realistic system sizes. The heating and acceleration process is very fast (\sim 2 s). The reason why the acceleration time is so short is that the particles are trapped within small scale parts of the fractal environment, and their scattering mean free path reduces drastically. The presence of small scale activity also pulls easily particles from the thermal pool, so there is no need for a seed population. The mean square displacement in space and energy is superdiffusive for the high energy particles.
