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arXiv 2107.01546astro-ph.SRastro-ph.IM
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Babcock-Leighton型运动发电机模型中的亚临界发电机和滞后

Subcritical dynamo and hysteresis in a Babcock-Leighton type kinematic dynamo model

Vindya Vashishth, Bidya Binay Karak, Leonid Kitchatinov

摘要:

在太阳和类太阳恒星中,对流区等离子体流中的差旋和螺旋度的存在导致了大尺度磁场的周期性。因此,对于每一颗恒星,都有一个临界发电机数来维持一个大规模发电机的运转。当恒星减速时,预计大规模发电机将在临界旋转周期以上停止运行。在我们的研究中,我们探讨的可能性,操作的发电机在亚临界区使用Babcock-Leighton型运动发电机模型。在某些参数区域,我们发现发电机表现出滞后行为,即,两个发电机解决方案是可能的,这取决于初始参数-衰减的解决方案,如果开始与弱场和强振荡的解决方案(亚临界发电机),当开始与强场。然而,在发电机参数的大波动下,亚临界发电机模式在某些参数区域是不稳定的。因此,我们的研究支持可能存在的亚临界发电机在某些恒星,这是以前所示的平均场发电机模型与分布式$α$和MHD湍流发电机模拟。

英文摘要:

In Sun and sun-like stars, it is believed that the cycles of the large-scale magnetic field are produced due to the existence of differential rotation and helicity in the plasma flows in their convection zones (CZs). Hence, it is expected that for each star, there is a critical dynamo number for the operation of a large-scale dynamo. As a star slows down, it is expected that the large-scale dynamo ceases to operate above a critical rotation period. In our study, we explore the possibility of the operation of the dynamo in the subcritical region using the Babcock--Leighton type kinematic dynamo model. In some parameter regimes, we find that the dynamo shows hysteresis behavior, i.e., two dynamo solutions are possible depending on the initial parameters -- decaying solution if started with weak field and strong oscillatory solution (subcritical dynamo) when started with a strong field. However, under large fluctuations in the dynamo parameter, the subcritical dynamo mode is unstable in some parameter regimes. Therefore, our study supports the possible existence of subcritical dynamo in some stars which was previously shown in a mean-field dynamo model with distributed $α$ and MHD turbulent dynamo simulations.

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