DIFFUSIVE COSMIC RAY ACCELERATION AT RELATIVISTIC SHOCK WAVES WITH MAGNETOSTATIC TURBULENCE. II. INFLUENCE OF A FINITE DOWNSTREAM MEDIUM
DIFFUSIVE COSMIC RAY ACCELERATION AT RELATIVISTIC SHOCK WAVES WITH MAGNETOSTATIC TURBULENCE. II. INFLUENCE OF A FINITE DOWNSTREAM MEDIUM
复制标题
DOI：
10.1088/0004-637x/809/2/124
复制
发表时间：
2015-03
期刊：
影响因子：
--
通讯作者：
T. Antecki;R. Schlickeiser;S. Krakau
中科院分区：
文献类型：
--
作者：
T. Antecki;R. Schlickeiser;S. Krakau
研究了相对论性宇宙射线在具有静磁湍流和有限尺寸下游介质的平行激波中的扩散加速度。对于具有洛伦兹因子的超相对论性激波速度，激波处的微分动量谱和体积积分动量谱都是与无限扩展的下游介质情况不同的幂律分布函数。然而，与非相对论性激波相比，谱上的差异并不大。激波加速粒子的动量谱行为敏感地取决于相对论性激波佩莱特数，即宇宙射线从激波位置传播到下游边界z0的扩散和对流时间尺度之比。对于较大值的自由逃逸边界，对粒子加速的有效性没有影响，仍然提供了被加速粒子的平坦动量幂律谱。在相反的情况下，在所有动量下的小Peclet数，激波处的动量谱陡增到更大的谱指数，而体积积分动量谱因其幂律谱指数相同的因素而变平，其中s表示静磁湍流下游功率谱的谱指数。相对论性激波在产生平坦的幂律动量谱方面的有效性与非相对论性激波的行为完全不同。
The diffusive acceleration of relativistic cosmic rays at parallel shock waves with magnetostatic turbulence and a finite size of the downstream medium is investigated. For ultrarelativistic shock speeds with Lorentz factor , both the differential momentum spectrum at the shock and the volume-integrated momentum spectrum are power-law distribution functions with different spectral indices as compared to the case of an infinitely extended downstream medium. However, the spectral differences are only modest as compared to the case of nonrelativistic shocks. The behavior of the momentum spectrum of shock-accelerated particles depends sensitively on the relativistic shock wave Peclet number , i.e., the ratio between the diffusion and convection timescales of cosmic rays to propagate from the shock position to the downstream boundary z0. For large values of the free-escape boundary has no influence on the effectiveness of particle acceleration, still providing a flat momentum power-law spectrum of the accelerated particles. In the opposite case of small Peclet numbers at all momenta, the momentum spectrum at the shock steepens to the greater spectral index , whereas the volume-integrated momentum spectrum flattens by the same factor for its power-law spectral index, where s denotes the spectral index of the downstream power spectrum of magnetostatic turbulence. This effectiveness of relativistic shocks in generating flat power-law momentum spectra irrespective of the Peclet number differs completely from the behavior of nonrelativistic shocks.