A new solar cycle model including meridional circulation
A new solar cycle model including meridional circulation
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DOI：
10.1086/170800
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发表时间：
1991-12
期刊：
影响因子：
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通讯作者：
Yan Wang;N. Sheeley;A. Nash
中科院分区：
文献类型：
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作者：
Yan Wang;N. Sheeley;A. Nash
一个运动学模型的太阳活动周期，其中不仅包括运输的磁通量的超颗粒扩散和极地散装流在太阳的表面，但也湍流扩散和赤道的“回流”的影响下的表面。在Babcock和Leighton的早期模型中，地下极向场的旋转剪切产生了环形通量，以双极磁区的形式在地表爆发。然而，这样的爆发不会导致任何来自太阳的环向通量的净损失（如Babcock和Leighton所假设的那样）;相反，大规模的环向场被破坏，既因为局部极向场反转其极性而被“解绕”，也因为环向通量被地下流向赤道输送并与其相对的半球对应物合并而被扩散。包含的纬向环流允许稳定的磁场振荡，伴随着赤道进展的通量爆发，即使在角速度的径向梯度的情况下也可以实现。一个说明性的情况下，地下水流速度的顺序1米/秒和地下扩散率的顺序10平方公里/秒产生22年的振荡与观测定性协议。
A kinematic model is presented for the solar cycle which includes not only the transport of magnetic flux by supergranular diffusion and a poleward bulk flow at the sun's surface, but also the effects of turbulent diffusion and an equatorward 'return flow' beneath the surface. As in the earlier models of Babcock and Leighton, the rotational shearing of a subsurface poloidal field generates toroidal flux that erupts at the surface in the form of bipolar magnetic regions. However, such eruptions do not result in any net loss of toroidal flux from the sun (as assumed by Babcock and Leighton); instead, the large-scale toroidal field is destroyed both by 'unwinding' as the local poloidal field reverses its polarity, and by diffusion as the toroidal flux is transported equatorward by the subsurface flow and merged with its opposite hemisphere counterpart. The inclusion of meridional circulation allows stable oscillations of the magnetic field, accompanied by the equatorward progression of flux eruptions, to be achieved even in the absence of a radial gradient in the angular velocity. An illustrative case in which a subsurface flow speed of order 1 m/s and subsurface diffusion rate of order 10 sq km/s yield 22-yr oscillations in qualitative agreement with observations.