KINETIC SIMULATIONS OF TURBULENT MAGNETIC-FIELD GROWTH BY STREAMING COSMIC RAYS
KINETIC SIMULATIONS OF TURBULENT MAGNETIC-FIELD GROWTH BY STREAMING COSMIC RAYS
复制标题
通过宇宙射线流进行湍流磁场增长的动力学模拟
DOI：
10.1088/0004-637x/706/1/38
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发表时间：
2009
期刊：
影响因子：
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通讯作者：
J. Niemiec
中科院分区：
文献类型：
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作者：
T. Stroman;M. Pohl;J. Niemiec
宇宙射线的有效加速（通过扩散激波加速的机制）需要激波上游区域的湍流放大磁场。我们提出了多维粒子模拟的结果，旨在观察磁场放大，预计将出现从宇宙射线电流的冲击，上游星际介质的属性的影响。我们发现，放大场的初始结构和峰值强度对参数的选择有些敏感，但场的增长在所有情况下都以类似的方式饱和：宇宙射线的反作用导致其静止坐标系分布的改变以及向星际介质的动量净转移，大大削弱了它们的相对漂移，同时也意味着一个修改后的冲击的发展。上游介质变得湍流，密度和速度有明显的空间波动，特别是后者导致适度的上游加热;这种波动也将对激波结构产生强烈的影响。
Efficient acceleration of cosmic rays (via the mechanism of diffusive shock acceleration) requires turbulent, amplified magnetic fields in the shock's upstream region. We present results of multidimensional particle-in-cell simulations aimed at observing the magnetic field amplification that is expected to arise from the cosmic-ray current ahead of the shock, and the impact on the properties of the upstream interstellar medium. We find that the initial structure and peak strength of the amplified field are somewhat sensitive to the choice of parameters, but that the field growth saturates in a similar manner in all cases: the back-reaction on the cosmic rays leads to modification of their rest-frame distribution and also a net transfer of momentum to the interstellar medium, substantially weakening their relative drift while also implying the development of a modified shock. The upstream medium becomes turbulent, with significant spatial fluctuations in density and velocity, the latter in particular leading to moderate upstream heating; such fluctuations will also have a strong influence on the shock structure.