辐射主导的吸积盘局部模拟中的湍流应力和Lightman-Eardley不稳定性的可能性
Turbulent Stresses in Local Simulations of Radiation-Dominated Accretion Disks, and the Possibility of the LIghtman-Eardley Instability
摘要：
我们提出了一系列的辐射MHD模拟的结果的局部补丁的吸积盘，具有固定的垂直重力剖面，但具有不同的表面质量密度和广泛的辐射气体压力比。每个模拟都实现了持续许多冷却时间的热平衡。在与冷却时间相比长的时间内平均后，我们发现垂直积分应力与垂直平均总热（气体加辐射）压力近似成比例。我们绘制出-第一次明确的物理学的基础上-应力和表面密度之间的热平衡关系：应力减少（增加）与增加表面质量密度时，模拟辐射（气体）压力占主导地位。在辐射压力主导的区域中，应力对表面质量密度的依赖性表明可能存在Lightman-Eardley入流不稳定性，但需要使用更宽的径向箱进行全局模拟或剪切箱模拟，以确认这一点并确定其非线性行为。
英文摘要：
We present the results of a series of radiation-MHD simulations of a local patch of an accretion disk, with fixed vertical gravity profile but with different surface mass densities and a broad range of radiation to gas pressure ratios. Each simulation achieves a thermal equilibrium that lasts for many cooling times. After averaging over times long compared to a cooling time, we find that the vertically integrated stress is approximately proportional to the vertically-averaged total thermal (gas plus radiation) pressure. We map out--for the first time on the basis of explicit physics--the thermal equilibrium relation between stress and surface density: the stress decreases (increases) with increasing surface mass density when the simulation is radiation (gas) pressure dominated. The dependence of stress on surface mass density in the radiation pressure dominated regime suggests the possibility of a Lightman-Eardley inflow instability, but global simulations or shearing box simulations with much wider radial boxes will be necessary to confirm this and determine its nonlinear behavior.
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