The impact of astrophysical dust grains on the confinement of cosmic rays
The impact of astrophysical dust grains on the confinement of cosmic rays
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DOI：
10.1093/mnras/stab179
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发表时间：
2020-11
影响因子：
4.8
通讯作者：
J. Squire;P. Hopkins;E. Quataert;Philipp Kempski
中科院分区：
文献类型：
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作者：
J. Squire;P. Hopkins;E. Quataert;Philipp Kempski
我们认为，带电尘埃颗粒可能会显著影响星系宇宙射线的限制和传输。对于亚GeV到~ 103 GeV的宇宙射线，通过回旋共振相互作用使宇宙射线各向同性的小规模平行alfvsamn波也与带电粒子发生回旋共振。如果尘埃几乎是静止的，就像在大部分星际介质中一样，阿尔夫沙姆波就会被尘埃所抑制。这将降低宇宙射线通过流不稳定性产生的阿尔夫萨芬波的振幅，从而增强宇宙射线的传输。在电离良好的区域，尘埃阻尼率比其他机制在与~ GeV宇宙射线相关的尺度上阻尼平行alfvsamn波的系数大10倍，这表明尘埃可能在调节宇宙射线传输中发挥关键作用。在天体物理学的情况下，尘埃以超阿尔夫萨芬速度穿过气体，阿尔夫萨芬波变得不稳定，这可能会直接散射宇宙射线。这种相互作用有可能创造出一种强大的反馈机制，在这种机制中，尘埃在辐射压力的驱使下穿过气体，然后强烈地增强了对宇宙射线的限制，增加了它们驱动外流的能力。这种机制可能在恒星形成星系和活动星系核周围的星系周围介质中起作用。
We argue that charged dust grains could significantly impact the confinement and transport of galactic cosmic rays. For sub-GeV to ∼103 GeV cosmic rays, small-scale parallel Alfvén waves, which isotropize cosmic rays through gyro-resonant interactions, are also gyro-resonant with charged grains. If the dust is nearly stationary, as in the bulk of the interstellar medium, Alfvén waves are damped by dust. This will reduce the amplitude of Alfvén waves produced by the cosmic rays through the streaming instability, thus enhancing cosmic ray transport. In well-ionized regions, the dust damping rate is larger by a factor of ∼10 than other mechanisms that damp parallel Alfvén waves at the scales relevant for ∼GeV cosmic rays, suggesting that dust could play a key role in regulating cosmic ray transport. In astrophysical situations in which the dust moves through the gas with super-Alfvénic velocities, Alfvén waves are rendered unstable, which could directly scatter cosmic rays. This interaction has the potential to create a strong feedback mechanism where dust, driven through the gas by radiation pressure, then strongly enhances the confinement of cosmic rays, increasing their capacity to drive outflows. This mechanism may act in the circumgalactic medium around star-forming galaxies and active galactic nuclei.