Zhdankin Vladimir, Werner Gregory R, Uzdensky Dmitri A, Begelman Mitchell C
JILA, University of Colorado and NIST, 440 UCB, Boulder, Colorado 80309, USA.
Center for Integrated Plasma Studies, Physics Department, University of Colorado, 390 UCB, Boulder, Colorado 80309, USA.
Phys Rev Lett. 2017 Feb 3;118(5):055103. doi: 10.1103/PhysRevLett.118.055103.
We present results from particle-in-cell simulations of driven turbulence in magnetized, collisionless, and relativistic pair plasmas. We find that the fluctuations are consistent with the classical k_{⊥}^{-5/3} magnetic energy spectrum at fluid scales and a steeper k_{⊥}^{-4} spectrum at sub-Larmor scales, where k_{⊥} is the wave vector perpendicular to the mean field. We demonstrate the development of a nonthermal, power-law particle energy distribution f(E)∼E^{-α}, with an index α that decreases with increasing magnetization and increases with an increasing system size (relative to the characteristic Larmor radius). Our simulations indicate that turbulence can be a viable source of energetic particles in high-energy astrophysical systems, such as pulsar wind nebulae, if scalings asymptotically become insensitive to the system size.
我们展示了在磁化、无碰撞和相对论性电子-正电子等离子体中驱动湍流的粒子模拟结果。我们发现，在流体尺度上，涨落与经典的(k_{⊥}^{-5/3})磁能谱一致，而在亚拉莫尔尺度上则是更陡的(k_{⊥}^{-4})谱，其中(k_{⊥})是垂直于平均场的波矢。我们证明了非热幂律粒子能量分布(f(E)∼E^{-α})的发展，指数(α)随着磁化强度的增加而减小，并随着系统尺寸（相对于特征拉莫尔半径）的增加而增加。我们的模拟表明，如果标度渐近地对系统尺寸不敏感，那么湍流可以成为高能天体物理系统（如脉冲星风星云）中高能粒子的一个可行来源。
