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arXiv 1909.06346astro-ph.HEphysics.plasm-ph
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共振和非共振Cosmic Ray流动不稳定性的混合模拟

Hybrid Simulations of the Resonant and Non-Resonant Cosmic Ray Streaming Instability

Colby Haggerty, Damiano Caprioli, Ellen Zweibel

摘要:

使用混合模拟(动力学离子-流体电子),我们测试宇宙射线(CR)流不稳定性的线性理论预测。我们考虑两种类型的CR分布函数:一个“热”的分布,其中CR是由一个漂移的幂律动量和各向异性的“光束”的单色粒子。此外,对于每个CR分布,我们扫描不同的CR密度,从触发共振到非共振(贝尔)流不稳定性的过渡。我们确定这些不稳定性的增长率在模拟拟合的指数曲线在线性阶段,我们表明,他们同意以及作为波数的函数的理论预测一致。我们还研究了作为时间和波数的函数的磁螺旋度,发现与预测的一般良好的协议,以及一些意想不到的非线性特征的不稳定性发展。

英文摘要:

Using hybrid simulations (kinetic ions--fluid electrons), we test the linear theory predictions of the cosmic ray (CR) streaming instability. We consider two types of CR distribution functions: a "hot" distribution where CRs are represented by a drifting power law in momentum and an anisotropic "beam" of monochromatic particles. Additionally, for each CR distribution we scan over different CR densities to transition from triggering the resonant to the non-resonant (Bell) streaming instability. We determine the growth rates of these instabilities in simulations by fitting an exponential curve during the linear stage, and we show that they agree well with the theoretical predictions as a function of wave number agree. We also examine the magnetic helicity as a function of time and wave number, finding a general good agreement with the predictions, as well as some unexpected non-linear features to the instability development.

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