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arXiv 2103.11754astro-ph.SRphysics.space-ph
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发电机的超临界性限制了极场的存储为一个周期

Supercriticality of the dynamo limits the memory of the polar field to one cycle

Pawan Kumar, Bidya Binay Karak, Vindya Vashishth

备注：
12 pages, 7 figures and accepted in ApJ
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摘要：

极地磁场前兆被认为是预测下一个太阳活动周期强度的最可靠和基于物理的方法。然而，为了对一个周期做出可靠的预测，前一个周期太阳极小期的极场是否足够，或者我们需要许多以前周期的极场？为了回答这个问题，我们进行了几次模拟使用Babcock-Leighton型通量输运发电机模型与随机强迫源的极向场（$α$项）。我们表明，当发电机是在临界发电机过渡或弱超临界附近运行时，周期n的极性场决定了接下来几个周期（至少三个）的振幅。然而，当发电机基本上是超临界时，极场的这种相关性减少到一个周期。随着发电机的超临界性的增加，极场的记忆从多周期到单周期的这种变化与模型中各种湍流传输过程的重要性无关。我们进一步表明，当发电机在临界点附近运行时，它会产生频繁的较弱活动的延长事件，类似于太阳的大极小期。巨极小的发生伴随着极场的多旋回相关。极大极小值的出现频率随发电机超临界度的增大而减小。

英文摘要：

The polar magnetic field precursor is considered to be the most robust and physics-based method for the prediction of the next solar cycle strength. However, to make a reliable prediction of a cycle, is the polar field at the solar minimum of the previous cycle enough or we need the polar field of many previous cycles? To answer this question, we performed several simulations using Babcock-Leighton type flux transport dynamo models with the stochastically forced source for the poloidal field ($α$ term). We show that when the dynamo is operating near the critical dynamo transition or only weakly supercritical, the polar field of the cycle n determines the amplitude of the next several cycles (at least three). However, when the dynamo is substantially supercritical, this correlation of the polar field is reduced to one cycle. This change in the memory of the polar field from multi- to one-cycle with the increase of the super-criticality of the dynamo is independent of the importance of various turbulent transport processes in the model. We further show that when the dynamo operates near the critical, it produces frequent extended episodes of weaker activity, resembling the solar grand minima. The occurrence of grand minima is accompanied by the multi-cycle correlation of polar field. The frequency of grand minima decreases with the increase of supercriticality of the dynamo.

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