辐射无效圆盘中的共转力矩
On the corotation torque in a radiatively inefficient disk
摘要：
本文考虑了二维气体圆盘与均匀旋转的外势场共转共振时的角动量交换，假定圆盘流动是绝热的。我们首先考虑一个孤立的共振的线性情况下，我们给出了一个表达式的共转扭矩，涉及的压力扰动，并减少到通常的依赖于涡度梯度在一个冷盘的限制。虽然这个表达式需要解决的流体动力学方程，它提供了一些洞察力的动力学的共转区域。在一般情况下，我们发现一个额外的依赖于熵梯度共转。这种依赖关系与熵扰动的平流有关。这些与压力扰动无关。他们仍然局限于共转区域，在那里他们产生一个单一的贡献的共转扭矩。在第二部分中，我们检查我们的扭矩表达式通过定制的二维流体动力学模拟。在第三部分，我们考虑的情况下，一颗行星嵌入开普勒磁盘，假设是绝热的。我们发现了一个过剩的共转扭矩的熵梯度的规模，我们检查的熵扰动的扭矩的贡献是在协议从线性分析得到的表达式。最后，我们讨论了在原行星盘的流动是辐射效率低的马蹄形U形转弯的时间尺度上的低质量行星的迁移的共转扭矩表达式的一些影响。
英文摘要：
We consider the angular momentum exchange at the corotation resonance between a two-dimensional gaseous disk and a uniformly rotating external potential, assuming that the disk flow is adiabatic. We first consider the linear case for an isolated resonance, for which we give an expression of the corotation torque that involves the pressure perturbation, and which reduces to the usual dependence on the vortensity gradient in the limit of a cold disk. Although this expression requires the solution of the hydrodynamic equations, it provides some insight into the dynamics of the corotation region. In the general case, we find an additional dependence on the entropy gradient at corotation. This dependence is associated to the advection of entropy perturbations. These are not associated to pressure perturbations. They remain confined to the corotation region, where they yield a singular contribution to the corotation torque. In a second part, we check our torque expression by means of customized two-dimensional hydrodynamical simulations. In a third part, we contemplate the case of a planet embedded in a Keplerian disk, assumed to be adiabatic. We find an excess of corotation torque that scales with the entropy gradient, and we check that the contribution of the entropy perturbation to the torque is in agreement with the expression obtained from the linear analysis. We finally discuss some implications of the corotation torque expression for the migration of low mass planets in the regions of protoplanetary disks where the flow is radiatively inefficient on the timescale of the horseshoe U-turns.
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