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arXiv 1005.2283astro-ph.SR
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Babcock-Leighton通量输运发电机模型中浮力引起的时滞

Buoyancy-induced time delays in Babcock-Leighton flux-transport dynamo models

L. Jouve, M. R. E. Proctor, G. Lesur

摘要:

太阳是一颗磁星,其周期性活动被认为与内部发电机机制有关。数值模拟与各种复杂程度的组合是一个有效和准确的工具,调查这样复杂的动力学过程。我们调查的磁浮力过程中的作用,在2D巴布科克-莱顿发电机模型,更准确地模拟极向场的表面源项。方法.要做到这一点,我们重新引入平均场模型的结果,全三维MHD计算的非线性演化的上升通量管在对流壳。更具体地说,Babcock-Leighton源项进行修改,以考虑到延迟引入的环形结构的上升时间从对流区的底部到太阳表面。我们发现,在方程中引入的时间延迟产生大的周期振幅的时间调制,即使在强大的,从而迅速上升的通量管被认为是。太阳周期的非周期调制出现在一系列典型的非线性系统的倍周期分叉之后。强的影响,即使由小延迟被发现是由于依赖的对流区的底部的磁场强度的延迟,调制少得多时,时间延迟保持不变。我们没有发现任何显着的影响,除了当延迟的周期是人为的强大。揭示了太阳周期变化的一个可能的新起源。这种调制的活动和由此产生的蝴蝶图比标准的巴布科克-莱顿模型产生的更符合观测结果。

英文摘要:

The Sun is a magnetic star whose cyclic activity is thought to be linked to internal dynamo mechanisms. A combination of numerical modelling with various levels of complexity is an efficient and accurate tool to investigate such intricate dynamical processes. We investigate the role of the magnetic buoyancy process in 2D Babcock-Leighton dynamo models, by modelling more accurately the surface source term for poloidal field. Methods. To do so, we reintroduce in mean-field models the results of full 3D MHD calculations of the non-linear evolution of a rising flux tube in a convective shell. More specifically, the Babcock-Leighton source term is modified to take into account the delay introduced by the rise time of the toroidal structures from the base of the convection zone to the solar surface. We find that the time delays introduced in the equations produce large temporal modulation of the cycle amplitude even when strong and thus rapidly rising flux tubes are considered. Aperiodic modulations of the solar cycle appear after a sequence of period doubling bifurcations typical of non-linear systems. The strong effects introduced even by small delays is found to be due to the dependence of the delays on the magnetic field strength at the base of the convection zone, the modulation being much less when time delays remain constant. We do not find any significant influence on the cycle period except when the delays are made artificially strong. A possible new origin of the solar cycle variability is here revealed. This modulated activity and the resulting butterfly diagram are then more compatible with observations than what the standard Babcock-Leighton model produces.

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