Cosmic-ray generated bubbles around their sources
Cosmic-ray generated bubbles around their sources
复制标题
宇宙射线在其源头周围产生气泡
DOI：
10.1093/mnras/stac466
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发表时间：
2022
影响因子：
4.8
通讯作者：
Blasi, P.
中科院分区：
文献类型：
--
作者：
Schroer, B.;Pezzi, O.;Caprioli, D.;Haggerty, C. C.;Blasi, P.
宇宙射线（CR）被认为是逃离他们的来源流沿着当地磁场线。我们表明，这种现象通常会导致激发共振和非共振流不稳定性。自生的磁场涨落在源周围的扩展区域中诱导粒子扩散，使得CR建立大的压力梯度。通过二维（2D）和三维（3D）的混合粒子在细胞中的模拟，我们表明，这样的压力梯度挖掘源周围的空腔，并导致宇宙射线占主导地位的气泡的形成，其中扩散率被强烈抑制。根据自洽模拟提取的趋势，我们估计，在没有严重阻尼的自生磁场，气泡应该保持膨胀，直到达到与周围介质的压力平衡，对应于半径为10-50 pc。这些地区的低扩散源的银河CR的形成的影响进行了讨论。特别注意的是，致力于估计自生扩散系数和克重，CR可能会积累在气泡移动到星际介质之前。基于三维模拟的结果，对这些扩展区域的γ射线和同步辐射的形态也进行了概述。
Cosmic rays (CRs) are thought to escape their sources streaming along the local magnetic field lines. We show that this phenomenon generally leads to the excitation of both resonant and non-resonant streaming instabilities. The self-generated magnetic fluctuations induce particle diffusion in extended regions around the source, so that CRs build up a large pressure gradient. By means of two-dimensional (2D) and three-dimensional (3D) hybrid particle-in-cell simulations, we show that such a pressure gradient excavates a cavity around the source and leads to the formation of a cosmic ray dominated bubble, inside which diffusivity is strongly suppressed. Based on the trends extracted from self-consistent simulations, we estimate that, in the absence of severe damping of the self-generated magnetic fields, the bubble should keep expanding until pressure balance with the surrounding medium is reached, corresponding to a radius of ∼10–50 pc. The implications of the formation of these regions of low diffusivity for sources of Galactic CRs are discussed. Special care is devoted to estimating the self-generated diffusion coefficient and the grammage that CRs might accumulate in the bubbles before moving into the interstellar medium. Based on the results of 3D simulations, general considerations on the morphology of the γ-ray and synchrotron emission from these extended regions also are outlined.