A Heating Mechanism via Magnetic Pumping in the Intracluster Medium
A Heating Mechanism via Magnetic Pumping in the Intracluster Medium
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DOI：
10.3847/1538-4357/acb3b1
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发表时间：
2022-08
期刊：
影响因子：
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通讯作者：
F. Ley;E. Zweibel;M. Riquelme;L. Sironi;Drake Miller;A. Tran
中科院分区：
文献类型：
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作者：
F. Ley;E. Zweibel;M. Riquelme;L. Sironi;Drake Miller;A. Tran
由活动星系核活动、星团合并和星系运动驱动的湍流构成了加热星系团内介质(ICM)的一个有吸引力的能量来源。考虑到ICM等离子体的低碰撞性和高磁化强度(排除了库仑过程的粘性加热)，这种能量是如何消散到ICM等离子体中的尚不清楚。Kunz等人的研究。提出了一种基于ICM条件下等离子体压力各向异性的可行加热机制。本论文建立在这项工作的基础上，并证明了粒子可以通过磁泵被大范围的湍流涨落加热。我们研究了各向异性如何在一定的强迫频率范围内演化，产生了什么波和不稳定性，并证明了粒子分布函数具有高能尾部。为此，我们执行粒子单元模拟，其中我们周期性地改变平均磁场B(T)。当B(T)增大(减小)时，压力各向异性P⊥>；P∥(P⊥P∥)和倾斜消防管(P∥>；P⊥)不稳定，它们捕获和散射粒子，限制各向异性，并提供加热等离子体的通道。这种机制的效率取决于大尺度湍流涨落的频率和不稳定性在其非线性阶段提供的散射的效率。我们提供了一个简化的分析加热模型，它捕捉到了所涉及的现象学。我们的结果表明，这一过程可能与ICM中运动尺度上的湍流能量耗散和分配有关。
Turbulence driven by active galactic nuclei activity, cluster mergers, and galaxy motion constitutes an attractive energy source for heating the intracluster medium (ICM). How this energy dissipates into the ICM plasma remains unclear, given its low collisionality and high magnetization (precluding viscous heating by Coulomb processes). Kunz et al. proposed a viable heating mechanism based on the anisotropy of the plasma pressure under ICM conditions. The present paper builds upon that work and shows that particles can be heated by large-scale turbulent fluctuations via magnetic pumping. We study how the anisotropy evolves under a range of forcing frequencies, what waves and instabilities are generated, and demonstrate that the particle distribution function acquires a high-energy tail. For this, we perform particle-in-cell simulations where we periodically vary the mean magnetic field B (t). When B (t) grows (dwindles), a pressure anisotropy P ⊥ > P ∥(P ⊥ P ∥) and oblique firehose (P ∥ > P ⊥) instabilities, which trap and scatter the particles, limiting the anisotropy, and providing a channel to heat the plasma. The efficiency of this mechanism depends on the frequency of the large-scale turbulent fluctuations and the efficiency of the scattering the instabilities provide in their nonlinear stage. We provide a simplified analytical heating model that captures the phenomenology involved. Our results show that this process can be relevant in dissipating and distributing turbulent energy at kinetic scales in the ICM.