Three-dimensional Simulations of Magnetospheric Accretion in a T Tauri Star: Accretion and Wind Structures Just Around the Star
Three-dimensional Simulations of Magnetospheric Accretion in a T Tauri Star: Accretion and Wind Structures Just Around the Star
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DOI：
10.3847/1538-4357/ac9eb1
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发表时间：
2022-11
期刊：
影响因子：
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通讯作者：
S. Takasao;K. Tomida;K. Iwasaki;T. Suzuki
中科院分区：
文献类型：
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作者：
S. Takasao;K. Tomida;K. Iwasaki;T. Suzuki
利用三维磁流体动力学方法模拟金牛座T型星星的磁层吸积过程，研究了该星星附近的吸积和风结构。吸积到星星上的气体包括来自磁层边界的气体和失效的盘风。吸积气体通常以多柱吸积的形式存在，这与观测结果一致。吸积流的角动量的一个显着的部分被删除的磁场的锥形盘风和湍流失败的风内部和附近的磁层。结果，与基于质量吸积率的简单估计相比，吸积扭矩显著减小。恒星自转通过改变磁层边界的稳定性条件来影响锥盘风的时变特性。然而，时间平均磁层半径仅微弱地依赖于恒星自旋，这与经典理论预测的恒星自旋通过磁矩控制磁层半径不同。磁层边界处的环向场与极向场的强度之比，是磁转矩的一个关键参数，对自旋也不敏感;它是由磁盘动力学决定的。考虑到新发现的3D效应，我们从稳态角动量输运方程中获得了与Ghosh & Lamb关系非常相似的磁层半径标度关系。
We perform three-dimensional (3D) magnetohydrodynamic simulations of magnetospheric accretion in a T Tauri star to study the accretion and wind structures in the close vicinity of the star. The gas accreting onto the star consists of the gas from the magnetospheric boundary and the failed disk winds. The accreting gas is commonly found as a multi-column accretion, which is consistent with observations. A significant fraction of the angular momentum of the accreting flows is removed by the magnetic fields of conical disk winds and turbulent failed winds inside and near the magnetosphere. As a result, the accretion torque is significantly reduced compared to the simple estimation based on the mass accretion rate. The stellar spin affects the time variability of the conical disk wind by changing the stability condition of the magnetospheric boundary. However, the time-averaged magnetospheric radius only weakly depends on the stellar spin, which is unlike the prediction of classical theories that the stellar spin controls the magnetospheric radius through the magnetic torque. The ratio of the toroidal to the poloidal field strengths at the magnetospheric boundary, which is a key parameter for the magnetic torque, is also insensitive to the spin; it is rather determined by the disk dynamics. Considering newly found 3D effects, we obtain a scaling relation of the magnetospheric radius very similar to the Ghosh & Lamb relation from the steady angular momentum transport equation.