The three-dimensional evolution of buoyant magnetic flux tubes in a model solar convective envelope
The three-dimensional evolution of buoyant magnetic flux tubes in a model solar convective envelope
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DOI：
10.1086/527317
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发表时间：
2008-03-20
影响因子：
4.9
通讯作者：
Fan, Y.
中科院分区：
文献类型：
--
作者：
Fan, Y.
我们提出了一套三维球壳滞弹性MHD模拟的浮力上升的磁通量管从对流区的底部到光球以下的深度为16毫米。研究发现，当一个扭曲的通量管拱向上由于浮力，它旋转出平面，从而产生一个倾斜的顶点。我们的模拟结果表明，对于扭转率为内聚上升所必需的管道，扭转引起的倾斜占主导地位，由科里奥利力引起的倾斜，而且，扭转引起的倾斜是错误的方向（与观测的乔伊定律相反）如果扭曲是左手的，（右利手）在北方（南）半球，遵循观察到的活动区域扭曲的符号的半球偏好。据发现，为了新兴管显示正确的倾斜方向（与观测一致），磁通管的初始扭曲率需要小于内聚上升所需的一半。在这种情况下，严重的磁通损失期间发现上升。我们还发现，由于由科里奥利力的上升管的不对称拉伸，场强不对称的发展，与在Ω形新兴管的领先腿（在旋转方向领先）的字段比在以下腿中的字段更强，这导致在新兴的活动区域的领先极性中的更紧凑的形态。
We present a set of three-dimensional spherical shell anelastic MHD simulations of the buoyant rise of magnetic flux tubes from the base of the convection zone to a depth of 16 Mm below the photosphere. It is found that when a twisted flux tube arches upward due to buoyancy, it rotates out of the plane and thus produces a tilt at the apex. Our simulations show that for tubes with the twist rate that is necessary for a cohesive rise, the twist-induced tilt dominates that caused by the Coriolis force, and furthermore, the twist-induced tilt is of the wrong direction (opposite to the observational Joy's law) if the twist is left-handed (right-handed) in the northern (southern) hemisphere, following the observed hemispheric preference of the sign of the active region twist. It is found that in order for the emerging tube to show the correct tilt direction (consistent with observations), the initial twist rate of the flux tube needs to be less than half of that needed for a cohesive rise. Under such conditions, severe flux loss is found during the rise. We also found that due to the asymmetric stretching of the rising tube by the Coriolis force, a field strength asymmetry develops, with the field in the leading leg (leading in the direction of rotation) of the Omega-shaped emerging tube being stronger than the field in the following leg, which results in a more compact morphology in the leading polarity of the emerging active region.