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The Orientational Relaxation of Bipolar Active Regions

机译：双极有源区的方向弛豫

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摘要

In the mean, bipolar active regions are oriented nearly toroidally, according to Hale's polarity law, with a latitude-dependent tilt known as Joy's Law. The tilt angles of individual active regions deviate from this mean behavior and change over time. It has been found that on average the change is toward the mean angle at a rate characteristic of 4.37 days (Howard, 1996). We show that this orientational relaxation is consistent with the standard model of flux tube emergence from a deep dynamo layer. Under this scenario Joy's law results from the Coriolis effect on the rising flux tube (D'Silva and Choudhuri, 1993), and departures from it result from turbulent buffeting of the tubes (Longcope and Fisher, 1996). We show that relaxation toward Joy's angle occurs because the turbulent perturbations relax on shorter time scales than the perturbations from the Coriolis force. The turbulent perturbations relax more rapidly because they are localized to the topmost portion of the convection zone while the Coriolis perturbations are more widely distributed. If a fully-developed active region remains connected to the strong toroidal magnetic field at the base of the convection zone, its tilt will eventually disappear, leaving it aligned perfectly toroidally. On the other hand, if the flux becomes disconnected from the toroidal field the bipole will assume a tilt indicative of the location of disconnection. We compare models which are connected and disconnected from the toroidal field. Only those disconnected at points very deep in the convection zone are consistent with observed time scale of orientational relaxation.
机译：平均而言，根据Hale的极性定律，双极有源区几乎呈环形取向，并具有与纬度相关的倾斜，即乔伊定律。各个有源区域的倾斜角均偏离该平均行为，并随时间变化。已经发现，平均而言，该变化以4.37天的速率特征朝向平均角度变化（Howard，1996）。我们表明，这种定向弛豫与从深层发电机流出来的通量管的标准模型是一致的。在这种情况下，乔伊定律是由对上升的通量管的科里奥利效应引起的（D'Silva和Choudhuri，1993），而偏离则是由于管的湍流颤动引起的（Longcope和Fisher，1996）。我们证明了发生向乔伊角的松弛是因为湍流扰动比科里奥利力的扰动在更短的时间尺度上松弛。湍流扰动更加迅速地松弛，因为它们位于对流区的最顶部，而科里奥利扰动分布更广。如果一个完全发达的有源区域保持与对流区底部的强环形磁场连接，则其倾斜将最终消失，从而使其完美地呈环形排列。另一方面，如果磁通量与环形磁场断开，则双极将采取指示断开位置的倾斜角度。我们比较了与环形场连接和断开的模型。只有那些在对流区深处断开的点才与观测到的定向弛豫时间尺度一致。

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  • 来源
    《Solar Physics》 |2002年第1期|63-92|共30页
  • 作者

    Dana Longcope; Arnab Rai Choudhuri;

  • 作者单位

    Department of Physics Montana State University;

    Department of Physics Indian Institute of Science;

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