Magnetorotational Instability in Eccentric Disks
Magnetorotational Instability in Eccentric Disks
复制标题
DOI：
10.3847/1538-4357/aab15c
复制
发表时间：
2017-12
期刊：
影响因子：
--
通讯作者：
C. Chan;J. Krolik;T. Piran
中科院分区：
文献类型：
--
作者：
C. Chan;J. Krolik;T. Piran
偏心盘出现在潮汐破裂事件等天体物理学背景下，但目前尚不清楚在圆盘中为吸积提供动力的磁旋转不稳定性（MRI）是否也在偏心盘中起作用。我们研究的线性演化的非分层，不可压缩的MRI在一个偏心盘绕一个点质量。我们考虑在具有均匀偏心率e和沿沿着平均运动为n的轨道的垂直阿尔文速度的背景流上的波数k的垂直模态。我们发现两个模式的家庭，一个占主导地位的磁分量，其他占主导地位的速度分量。前者在，where不稳定，后者在e 0.8不稳定。对于f2 <$3，磁共振成像表现得很像在圆盘中，但每个轨道的增长随着e的增加而缓慢下降;对于f2 <$3，模式通过参数放大而增长，这在0 < e <$1时是共振的。磁共振成像的增长和随之而来的角动量和能量传输主要发生在近心点附近，在那里轨道剪切主导磁张力。
Eccentric disks arise in such astrophysical contexts as tidal disruption events, but it is unknown whether the magnetorotational instability (MRI), which powers accretion in circular disks, operates in eccentric disks as well. We examine the linear evolution of unstratified, incompressible MRI in an eccentric disk orbiting a point mass. We consider vertical modes of wavenumber k on a background flow with uniform eccentricity e and vertical Alfvén speed along an orbit with mean motion n. We find two mode families, one with dominant magnetic components, the other with dominant velocity components. The former is unstable at , where , and the latter at e ≳ 0.8. For f2 ≲ 3, MRI behaves much like in circular disks, but the growth per orbit declines slowly with increasing e; for f2 ≳ 3, modes grow by parametric amplification, which is resonant for 0 < e ≪ 1. MRI growth and the attendant angular momentum and energy transport happen chiefly near pericenter, where orbital shear dominates magnetic tension.