Roberg-Clark G T, Drake J F, Reynolds C S, Swisdak M
Department of Physics, University of Maryland College Park, College Park, Maryland 20740, USA.
Institute for Physical Science and Technology, University of Maryland, College Park, Maryland 20742, USA.
Phys Rev Lett. 2018 Jan 19;120(3):035101. doi: 10.1103/PhysRevLett.120.035101.
The dynamics of weakly magnetized collisionless plasmas in the presence of an imposed temperature gradient along an ambient magnetic field is explored with particle-in-cell simulations and modeling. Two thermal reservoirs at different temperatures drive an electron heat flux that destabilizes off-angle whistler-type modes. The whistlers grow to large amplitude, δB/B_{0}≃1, and resonantly scatter the electrons, significantly reducing the heat flux. Surprisingly, the resulting steady-state heat flux is largely independent of the thermal gradient. The rate of thermal conduction is instead controlled by the finite propagation speed of the whistlers, which act as mobile scattering centers that convect the thermal energy of the hot reservoir. The results are relevant to thermal transport in high-β astrophysical plasmas such as hot accretion flows and the intracluster medium of galaxy clusters.
利用粒子模拟和建模方法，研究了沿背景磁场存在外加温度梯度时弱磁化无碰撞等离子体的动力学特性。两个不同温度的热库驱动电子热流，使非角度哨声型模式失稳。哨声增长到很大的幅度，δB/B₀≃1，并与电子发生共振散射，显著降低热流。令人惊讶的是，最终的稳态热流在很大程度上与热梯度无关。相反，热传导速率由哨声的有限传播速度控制，哨声充当移动散射中心，对流热库的热能。这些结果与高β天体物理等离子体中的热传输有关，如热吸积流和星系团的团内介质。
