Funnel Flows from Disks to Magnetized Stars
Funnel Flows from Disks to Magnetized Stars
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DOI：
10.1086/339304
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发表时间：
2001-04
期刊：
影响因子：
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通讯作者：
A. V. Koldoba;R. Lovelace;G. V. Ustyugova;M. Romanova
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文献类型：
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作者：
A. V. Koldoba;R. Lovelace;G. V. Ustyugova;M. Romanova
这项工作考虑了吸积盘与旋转恒星的对齐偶极磁场旋转的流动。假设理想磁流体力学（MHD）的压力和密度关系为p∝ργ， ρ2≪2/4π，其中为流速。跨音速流，即从靠近圆盘的亚音速运动到靠近恒星的超音速流入，仅在Rd ~ rc≡1/3的范围内是可能的，其中Rd是偶极子场线与圆盘相交的半径，rc是旋转半径，M是恒星的质量，Ω是它的角旋转速率。在较大的Rd > rc范围内，从盘到恒星的亚音速流动是可能的。γ bbb7 /5和γ 7/5的跨声速流表现出非常不同的行为，马赫数≡/cs（以cs为声速）在R从Rd开始减小时初始增大到1，但当R从≈0.22Rd开始减小时（当γ = 5/3时）马赫数减小，但仍保持在1。在γ < 7/5的另一个极限下，随着r的减小，λ γ γ δ γ单调增加，将这些结果应用于磁化中子星和年轻恒星物体的漏斗流。我们认为，在计算年轻恒星天体的发射线剖面时，需要包括旋转。
This work considers flows from an accretion disk corotating with the aligned dipole magnetic field of a rotating star. Ideal magnetohydrodynamics (MHD) is assumed with the pressure and density related as p ∝ ργ and with ρ2 ≪2/4π, where is the flow velocity. Transonic flows, which go from subsonic motion near the disk to supersonic inflow near the star, are shown to be possible only for a range of Rd ∼ rc ≡ 1/3, where Rd is the radius at which the dipole field line intersects the disk, rc is the corotation radius, M is the mass of the star, and Ω is its angular rotation rate. Over a larger range of Rd ≲ rc, subsonic flows from the disk to the star are possible. The transonic flows have very different behaviors for γ > 7/5 and γ 7/5, the Mach number ℳ ≡ /cs (with cs the sound speed) initially increases to values ≫1 with R decreasing from Rd, but for R decreasing from ≈0.22Rd (for γ = 5/3) the Mach number decreases while still being ≫1. In the other limit, γ < 7/5, ℳ increases monotonically with decreasing R. Application of these results is made to funnel flows to magnetized neutron stars and young stellar objects. We argue that the rotation needs to be included in the calculation of emission-line profiles of young stellar objects.