标题： 电子热力学在低光度黑洞吸积的GRMHD模拟中 显示英文标题

标题： Electron Thermodynamics in GRMHD Simulations of Low-Luminosity Black Hole Accretion

摘要： 关于电子热力学的简单假设通常限制了广义相对论磁流体动力学（GRMHD）模拟在低光度吸积黑洞观测中的应用程度。 我们提出、实现并测试了一个自洽地演化电子熵方程的模型，并考虑了沿磁场线的空间变化电子加热和相对论各向异性热传导的影响。 我们忽略了电子压力对吸积流动力学的反作用。 我们的模型适用于以$\ll 10^{-5}$倍爱丁顿率吸积的系统，因此可以忽略电子的辐射冷却。 未来可以通过包括电子冷却和质子-电子库仑碰撞来扩展到更高的吸积率。 我们展示了一套测试，表明我们的方法在各种情况下都能正确恢复电子加热的解，包括强激波和驱动湍流。 我们对吸积黑洞的轴对称模拟的初步应用显示，(1)~由物理动机得出的电子加热率会产生与之前工作中假设的恒定电子与质子温度比显著不同的电子温度分布，其中较高的电子温度集中在盘和喷流之间的冕区；(2)~如果有效电子平均自由程大于盘的局部尺度高度（至少对于我们研究的初始条件和磁场配置而言），电子热传导会显著改变黑洞吸积流内部区域的电子温度。 本工作中开发的方法对于产生更真实的吸积黑洞（如人马座A*和M87）的辐射预测非常重要；这些应用将在未来的工作中进行探索。 显示英文摘要

摘要： Simple assumptions made regarding electron thermodynamics often limit the extent to which general relativistic magnetohydrodynamic (GRMHD) simulations can be applied to observations of low-luminosity accreting black holes. We present, implement, and test a model that self-consistently evolves an electron entropy equation and takes into account the effects of spatially varying electron heating and relativistic anisotropic thermal conduction along magnetic field lines. We neglect the back-reaction of electron pressure on the dynamics of the accretion flow. Our model is appropriate for systems accreting at $\ll 10^{-5}$ of the Eddington rate, so radiative cooling by electrons can be neglected. It can be extended to higher accretion rates in the future by including electron cooling and proton-electron Coulomb collisions. We present a suite of tests showing that our method recovers the correct solution for electron heating under a range of circumstances, including strong shocks and driven turbulence. Our initial applications to axisymmetric simulations of accreting black holes show that (1)~physically-motivated electron heating rates yield electron temperature distributions significantly different from the constant electron to proton temperature ratios assumed in previous work, with higher electron temperatures concentrated in the coronal region between the disc and the jet; (2)~electron thermal conduction significantly modifies the electron temperature in the inner regions of black hole accretion flows if the effective electron mean free path is larger than the local scale-height of the disc (at least for the initial conditions and magnetic field configurations we study). The methods developed in this work are important for producing more realistic predictions for the emission from accreting black holes such as Sagittarius A* and M87; these applications will be explored in future work.