论文标题
声学$α$ -Disk
Acoustic $α$-disk
论文作者
论文摘要
结果表明，从磁盘的内边缘向外传播的声波的湍流会导致物质的积聚到中心。波的指数扩增发生在共振区域，$ω=（n \ pm 1）ω$。这里$ω$是声波的频率，$ n $是其方位角波数，$ω（r）$是磁盘旋转的角度频率。该效果类似于无碰撞等离子体中的Landau反向阻尼。能量来自磁盘旋转的能量。这导致磁盘角动量减少并增加物质。积聚率$ dm / dt $的值是$ {\ dot m} =πrc_sσ_0（c_s / v_ {ϕ0}）^2 w $。这里$ c_s $是磁盘气的声音速度，$ v_ {ϕ0} $是开普勒旋转速度，$σ_0$是磁盘的表面密度，$ w $是声学湍流的总功率{σ'} {σ_0} \ big {|}^2（ω，n）$，$ |σ'|^2（ω，n）$是湍流的频谱功能。提出的增生图片与观察到的X射线和光辐射的变化是一致的，这些物体的活性与气体上的积聚有关。
It is shown that the turbulent flow of acoustic waves propagating outward from the inner edge of the disk causes the accretion of the matter onto the center. The exponential amplification of waves takes place in the resonance region, $ ω= (n\pm 1)Ω$. Here $ ω$ is the frequency of the acoustic wave, $ n $ is its azimuthal wave number, $ Ω(r) $ is the angular frequency of rotation of the disk. The effect is similar to the inverse Landau damping in a collisionless plasma. Energy comes from the energy of rotation of the disk. That leads to decrease of the disk angular momentum and to accretion of the matter. The value of the accretion rate $dM/dt$ is ${\dot M} = πrc_s Σ_0 (c_s / v_{ϕ0})^2 W $. Here $ c_s $ is the speed of sound of the disk gas, $ v_{ϕ0} $ is the Keplerian rotation velocity, $Σ_0 $ is the surface density of the disk, $ W $ is total power of the acoustic turbulence, $ W \simeq \int_0^\infty d ω\sum_{n\geq 0} \Big {|} \frac {Σ'} {Σ_0} \Big {|}^2 (ω, n) $, $ |Σ'|^2 (ω, n) $ is the spectral power of turbulence. The presented picture of accretion is consistent with the observed variations of X-ray and optical radiation from objects whose activity is associated with accretion of gas onto them.
