Effect of a Magneto-Rotational Instability on Jets from Accretion Disks
Effect of a Magneto-Rotational Instability on Jets from Accretion Disks
复制标题
磁旋转不稳定性对吸积盘射流的影响
DOI：
10.1093/pasj/54.1.121
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发表时间：
2002
期刊：
影响因子：
--
通讯作者：
K. Shibata
中科院分区：
文献类型：
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作者：
T. Kudoh;R. Matsumoto;K. Shibata
我们提出了2.5维MHD模拟的结果，从吸积盘射流形成是不稳定的磁旋转不稳定。数值模拟表明，磁驱动射流是从磁旋转不稳定的圆盘中喷射出来的。喷流的速度与圆盘的开普勒速度相同。本文主要研究了磁旋转不稳定性对厚盘磁驱动射流的影响。为此，我们首先在一个由垂直均匀磁场缠绕的旋转圆盘上施加有限振幅的正弦摄动。磁旋转不稳定性增加了扰动，而磁旋转不稳定性的非线性发展导致通道流动，从而引起剧烈的吸积。随着吸积的继续，吸积流部分向外转向流出，并被沿极向磁场线的磁力加速，即产生磁驱动喷流。将初始有限振幅扰动模型（即|δv|/Vs = 0.1，其中δv为速度扰动，Vs为声速）与我们之前研究的没有任何扰动的模型进行比较。当扰动作用于盘内时，质量吸积率、质量抛射率和射流速度较大。然而，喷流速度与圆盘的开普勒速度差不多，几乎不受扰动的影响。
We present the results of 2.5-dimensional MHD simulations of jet formation from accretion disks that are unstable for a magneto-rotational instability. Numerical simulations show that magnetically driven jets are ejected from magneto-rotationally-unstable disks. The velocities of the jets are of the order of the Keplerian velocities of the disks. In this paper, we mainly focus on the effect of the magneto-rotational instability on magnetically driven jets from thick disks. For that purpose, we initially impose a sinusoidal perturbation with finite amplitude on a rotating disk that is threaded by a vertical uniform magnetic field. The perturbation grows by the magneto-rotational instability, and the nonlinear development of the instability leads to a channel flow which causes violent accretion. As the accretion continues, the accretion flow is partially turned outward to the outflow that is accelerated by the magnetic force along the poloidal magnetic field line, i.e., a magnetically driven jet is produced. Models with initial finite amplitude perturbation (i.e., |δv|/Vs = 0.1 where δv is the velocity perturbation and Vs is the sound velocity) are compared with those without any perturbation that we previously studied. The mass-accretion rate, mass-ejection rate, and jet velocity are larger when the perturbation is imposed on in the disk. However, the jet velocity is of the order of the Keplerian velocity of the disk, almost independent of the perturbation.