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arXiv 2209.08178astro-ph.SRphysics.plasm-ph
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双极磁区和太阳Babcock-Leighton发电机出现后演化的三维非运动学模拟

Three-dimensional non-kinematic simulation of post-emergence evolution of bipolar magnetic regions and Babcock-Leighton dynamo of the Sun

Yuto Bekki, Robert H. Cameron

摘要:

Babcock-Leighton(BL)通量输运模型是一个被广泛接受的太阳发电机模型。这个发电机模型已被广泛研究在一个二维(2D)的平均场框架中的运动和非运动制度。最近的三维(3D)模型已被限制到运动学制度。在这些模型中,表面极向通量是由根据乔伊定律倾斜的双极磁区(BMR)的出现产生的。我们调查处方出现的BMR在3D非运动学模拟。我们还报告了循环BL发电机模拟的初步结果。我们将传统的二维平均场模型扩展到三维非运动学区域。在该模式中,大尺度平均流由参数化的$Λ$效应驱动。对于感应方程,我们使用BL源项,通过该BL源项,表面BMR响应于对流区内部的发电机产生的环向场而产生。我们发现,在三维非运动学制度,倾斜角的新出现的BMR是非常敏感的处方的地下结构的BMR。反喜悦倾斜角被发现,除非BMR是深深地嵌入在对流区。我们还发现,领先的点往往变得比后面的点更强。反乔伊定律的趋势和形态的不对称性的BMR可以解释的科氏力作用于洛伦兹力驱动的流动。此外,我们还证明了如果在BL $α$效应中明确给出Joy定律,则可以成功地获得类太阳磁循环。在这些循环发电机模拟中,强洛伦兹力反馈导致差动旋转和双稳态循环中的循环调制。流的非轴对称分量被发现存在的惯性模式,如赤道Rossby模式。

英文摘要:

The Babcock-Leighton (BL) flux-transport model is a widely-accepted dynamo model of the Sun. This dynamo model has been extensively studied in a two-dimensional (2D) mean-field framework in both kinematic and non-kinematic regimes. Recent three-dimensional (3D) models have been restricted to the kinematic regime. In these models, the surface poloidal flux is produced by the emergence of bipolar magnetic regions (BMRs) that are tilted according to Joy's law. We investigate the prescription for emergence of a BMR in 3D non-kinematic simulations. We also report initial results of cyclic BL dynamo simulation. We extend a conventional 2D mean-field model of the BL flux-transport dynamo into 3D non-kinematic regime. The large-scale mean flows are driven by the parameterized $Λ$-effect in this model. For the induction equation, we use a BL source term by which the surface BMRs are produced in response to the dynamo-generated toroidal field inside the convection zone. We find that, in the 3D non-kinematic regime, the tilt angle of a newly-emerged BMR is very sensitive to the prescription for the subsurface structure of the BMR. Anti-Joy tilt angles are found unless the BMR is deeply embedded in the convection zone. We also find that the leading spot tends to become stronger than the following spot. The anti-Joy's law trend and the morphological asymmetry of the BMRs can be explained by the Coriolis force acting on the Lorentz-force-driven flows. Furthermore, we demonstrate that the solar-like magnetic cycles can be successfully obtained if the Joy's law is explicitly given in the BL $α$-effect. In these cyclic dynamo simulation, a strong Lorentz force feedback leads to cycle modulations in the differential rotation and meridional circulation. The non-axisymmetric components of the flows are found to exist as inertial modes such as the equatorial Rossby modes.

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