磁化吸积盘的不稳定性研究

Study on the Instability of Magnetized Accretion Disks

从磁流体动力学方程组出发,用微扰法得到的色散方程中含有环向磁场。利用全新的反常粘滞和反常阻抗,对吸积盘进行数值计算,结果表明,只有竖直方向的弱磁场才可以引发一种单调不稳定性。磁场对粘性吸积盘表现为非稳定性因素,增长率随磁场的增强而增大,且最大增长率大于理想情况下的值。垂向磁场足够强时,单调不稳定性不会出现。

Starting from the MHD equations,the dispersion formula including azimuthal magnetic field is derived from the perturbation method.Using the new anomalous viscosity and resistivity,the numerical result shows that only the vertical magnetic field can trigger a kind of monotonic instability.The magnetic field acts as a factor of instability for the viscous accretion disk.The growth rate grows as the magnetic field strengthens.Furthermore,the maximal growth rate is bigger than that of the ideal case.The monotonic instability will not emerge if the vertical magnetic field is strong enough.