A low upper limit on the subsurface rise speed of solar active regions.
A low upper limit on the subsurface rise speed of solar active regions.
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DOI：
10.1126/sciadv.1600557
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发表时间：
2016-07
期刊：
影响因子：
13.6
通讯作者：
Rempel M
中科院分区：
文献类型：
--
作者：
Birch AC;Schunker H;Braun DC;Cameron R;Gizon L;Löptien B;Rempel M
观测和模拟的比较为太阳活动区的地下上升速度提供了一个强有力的上限。磁场以太阳黑子和活动区的形式出现在太阳表面。这一过程从上升的环形通量管产生极向磁场；这是太阳能发电机的一个关键但鲜为人知的方面。磁场的出现也很重要，因为它是太阳活动的关键驱动力。我们表明，测量太阳表面围绕新出现的活动区的水平流动，结合太阳磁对流的数值模拟，可以限制新出现的磁通量的亚表面上升速度。观测到的流动表明，在20 mm的深度，磁场的上升速度不超过150m/S，即远低于(标准)薄通量管模型的预测值，但在该深度对流速度的预期范围内。我们的结论是，对流控制着太阳上层上升通量管的动力学，在通量涌现模型中不能忽略。
Comparison of observations and simulations provides a strong upper limit on the subsurface rise speed of solar active regions. Magnetic field emerges at the surface of the Sun as sunspots and active regions. This process generates a poloidal magnetic field from a rising toroidal flux tube; it is a crucial but poorly understood aspect of the solar dynamo. The emergence of magnetic field is also important because it is a key driver of solar activity. We show that measurements of horizontal flows at the solar surface around emerging active regions, in combination with numerical simulations of solar magnetoconvection, can constrain the subsurface rise speed of emerging magnetic flux. The observed flows imply that the rise speed of the magnetic field is no larger than 150 m/s at a depth of 20 Mm, that is, well below the prediction of the (standard) thin flux tube model but in the range expected for convective velocities at this depth. We conclude that convective flows control the dynamics of rising flux tubes in the upper layers of the Sun and cannot be neglected in models of flux emergence.