A Possible Route to Spontaneous Reduction of the Heat Conductivity by a Temperature Gradient-driven Instability in Electron-Ion Plasmas
A Possible Route to Spontaneous Reduction of the Heat Conductivity by a Temperature Gradient-driven Instability in Electron-Ion Plasmas
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电子离子等离子体中温度梯度驱动的不稳定性导致热导率自发降低的可能途径
DOI：
10.1086/308644
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
K. Umetsu
中科院分区：
文献类型：
--
作者：
M. Hattori;K. Umetsu
在等离子体动力学理论的框架下，通过线性摄动分析，我们证明了电子和离子等离子体中存在由全局温度梯度驱动的低频生长模式。不稳定性的驱动力是由于全局温度梯度引起的分布函数与麦克斯韦-玻尔兹曼分布的局部偏差。将结果应用于簇内介质时，比库仑碰撞产生的平均自由程小5-7个数量级。这可能为解释为什么在热导率为经典斯皮策值的情况下，尽管热传导导致蒸发时间很短，但热气体和冷气体在星系团内介质中可以共存提供了线索。我们的研究结果表明，局部不稳定延迟了整体热平衡的实现，而局部不稳定是为了更快地实现等离子体中的局部热平衡状态而引起的。这种不稳定性为在没有种子磁场的情况下创造和发展宇宙磁场提供了一种新的可能性。
We have shown that there exist low-frequency growing modes driven by a global temperature gradient in electron and ion plasmas by linear perturbation analysis within the framework of plasma kinetic theory. The driving force of the instability is the local deviation of the distribution function from the Maxwell-Boltzmann distribution due to a global temperature gradient. Application of the results to the intracluster medium is being reduced to 5-7 orders of magnitude less than the mean free paths due to Coulomb collisions. This may provide a hint in explaining why hot and cool gas can coexist in the intracluster medium in spite of the very short evaporation timescale due to thermal conduction if the conductivity is the classical Spitzer value. Our results suggest that the realization of the global thermal equilibrium is postponed by the local instability, which is induced for a quicker realization of the local thermal equilibrium state in plasmas. The instability provides a new possibility to create and grow cosmic magnetic fields without any seed magnetic field.