标题： 碰撞less等离子体中MRI的剪切盒模拟 显示英文标题

标题： Shearing Box Simulations of the MRI in a Collisionless Plasma

摘要： 我们描述了在无碰撞等离子体中由磁旋转不稳定性（MRI）驱动的湍流局域剪切盒模拟。无碰撞效应在辐射低效吸积流中可能很重要，例如银河系中心附近的黑洞附近。ZEUS的MHD版本被修改以演化各向异性压力张量。使用流体闭合近似来计算沿磁场线的热传导。各向异性压力张量为吸积流中的角动量输运提供了定性上新的机制（除了麦克斯韦和雷诺应力之外）。我们估计由于动能不稳定性引起的投射角散射对压力各向异性的限制。此类不稳定性在无碰撞等离子体中提供有效的“碰撞”率，并导致更类似于MHD的动力学。我们发现MRI在无碰撞等离子体中导致磁场的有效增长，饱和振幅与MHD相当。在饱和状态下，各向异性应力与麦克斯韦应力相当，这意味着角动量输运速率在无碰撞等离子体中可能会适度增强。 显示英文摘要

摘要： We describe local shearing box simulations of turbulence driven by the magnetorotational instability (MRI) in a collisionless plasma. Collisionless effects may be important in radiatively inefficient accretion flows, such as near the black hole in the Galactic Center. The MHD version of ZEUS is modified to evolve an anisotropic pressure tensor. A fluid closure approximation is used to calculate heat conduction along magnetic field lines. The anisotropic pressure tensor provides a qualitatively new mechanism for transporting angular momentum in accretion flows (in addition to the Maxwell and Reynolds stresses). We estimate limits on the pressure anisotropy due to pitch angle scattering by kinetic instabilities. Such instabilities provide an effective ``collision'' rate in a collisionless plasma and lead to more MHD-like dynamics. We find that the MRI leads to efficient growth of the magnetic field in a collisionless plasma, with saturation amplitudes comparable to those in MHD. In the saturated state, the anisotropic stress is comparable to the Maxwell stress, implying that the rate of angular momentum transport may be moderately enhanced in a collisionless plasma.