Convective collapse of flux tubes
Convective collapse of flux tubes
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DOI：
10.1007/bf00150420
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发表时间：
1979-03
期刊：
影响因子：
2.8
通讯作者：
H. Spruit
中科院分区：
文献类型：
--
作者：
H. Spruit
当表面场强小于1270 G时，垂直穿过太阳对流区的常数β通量管不稳定，达到对流不稳定。通过物质沿着管向下位移，不稳定的管可以转变成具有更高场强的具有更低能量的新的平衡状态。这些“崩溃”状态的数值计算。如果坍缩开始于一个强度与对流区动能均分相对应的场，它产生的表面场强度约为1650 G。提出活动区的小尺度磁场由这种管构成。塌缩状态不处于热平衡。在较深的层中，坍塌后的热交换非常缓慢，但表层迅速恢复到温度平衡。在坍缩态的热演化过程中，其表面层可能开始过稳振荡。在这种振荡的亮度速度相关性可以解释所观察到的下降气流的管。
Flux tubes of constant β extending vertically through the solar convection zone are unstable to a convective instability if the surface field strength is less than 1270 G. By downward displacement of matter along the tube an unstable tube can transform into a new equilibrium state with lower energy which has a higher field strength. Numerical calculations of these ‘collapsed’ states are presented. If the collapse starts in a field with a strength corresponding to equipartition with kinetic energy in the convection zone, it yields a surface field strength of about 1650 G. It is proposed that the small scale magnetic field in active regions consists of such tubes. The collapsed state is not in thermal equilibrium. In the deeper layers the heat exchange following the collapse is very slow but the surface layers return rapidly to temperature equilibrium. It is argued that during the gradual thermal evolution of the collapsed state its surface layers may start an overstable oscillation. A brightness-velocity correlation in this oscillation could account for the observed downdraft in the tubes.