Turbulent magnetic field amplification driven by cosmic ray pressure gradients
Turbulent magnetic field amplification driven by cosmic ray pressure gradients
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DOI：
10.1111/j.1365-2966.2012.22106.x
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发表时间：
2012-05
影响因子：
4.8
通讯作者：
L. Drury;T. Downes
中科院分区：
文献类型：
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作者：
L. Drury;T. Downes
对几个超新星遗迹的非热发射的观测表明，接近爆炸波的磁场比通过渗透星际介质（ISM）场的简单冲击压缩所天真的预期要强得多。我们提出了一个简单的模型，能够实现足够的磁场放大来解释观察结果。我们提出，作用于超新星爆炸波上游的不均匀ISM的宇宙射线压力梯度会在超新星爆炸波上游引起强烈的湍流。湍流是通过上游 ISM 的差分加速度产生的，这是由于 ISM 中的密度不均匀性而产生的。这种湍流会放大预先存在的磁场。数值模拟表明，当假设 ISM 和超新星爆炸波的合理参数时，通过该机制可以轻松实现 20 或更高的放大系数。发生这种放大的长度尺度是最高能量非热粒子的扩散长度。
Observations of non-thermal emission from several supernova remnants suggest that magnetic fields close to the blastwave are much stronger than would be naively expected from simple shock compression of the field permeating the interstellar medium (ISM). We present a simple model which is capable of achieving sufficient magnetic field amplification to explain the observations. We propose that the cosmic-ray pressure gradient acting on the inhomogeneous ISM upstream of the supernova blastwave induces strong turbulence upstream of the supernova blastwave. The turbulence is generatedthroughthedifferentialaccelerationoftheupstreamISMwhichoccursasaresult of density inhomogeneities in the ISM. This turbulence then amplifies the pre-existing magnetic field. Numerical simulations are presented which demonstrate that amplification factors of 20 or more are easily achievable by this mechanism when reasonable parameters for the ISM and supernova blastwave are assumed. The length scale over which this amplification occurs is that of the diffusion length of the highest energy non-thermal particles.