The stress-pressure lag in MRI turbulence and its implications for thermal instability in accretion discs
The stress-pressure lag in MRI turbulence and its implications for thermal instability in accretion discs
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MRI 湍流中的应力-压力滞后及其对吸积盘热不稳定性的影响
DOI：
10.1093/mnras/stab3398
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发表时间：
2022
影响因子：
4.8
通讯作者：
Held L
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作者：
Held L
经典的α-圆盘模型假设湍流应力与压力成线性比例，并对压力作出瞬时响应。然而，很可能应力具有不可忽略的弛豫时间，并且在某个时间尺度上将滞后于压力。为了测量这个滞后的大小，我们进行了非分层的3D磁流体力学剪切盒模拟零净磁通量使用有限体积codepluto。我们通过冷却项施加不同周期的热振荡，这反过来又驱动了湍流应力的振荡。我们的模拟表明，在振荡周期为几十个轨道或更长的情况下，应力振荡滞后于压力205个轨道。我们讨论了我们的结果的影响，在光盘周围的致密物体的热和粘性的超稳定性。
The classical alpha-disc model assumes that the turbulent stress scales linearly with – and responds instantaneously to – the pressure. It is likely, however, that the stress possesses a non-negligible relaxation time and will lag behind the pressure on some time-scale. To measure the size of this lag we carry out unstratified 3D magnetohydrodynamic shearing box simulations with zero-net-magnetic-flux using the finite-volume codepluto. We impose thermal oscillations of varying periods via a cooling term, which in turn drives oscillations in the turbulent stress. Our simulations reveal that the stress oscillations lag behind the pressure by ∼5 orbits in cases where the oscillation period is several tens of orbits or more. We discuss the implication of our results for thermal and viscous overstability in discs around compact objects.
松田卓也：皇家天文学会月刊（1987）。
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