论文标题
壳厚度对对流驱动的球形发电机中跨螺旋产生的影响
Effects of shell thickness on cross-helicity generation in convection-driven spherical dynamos
论文作者
论文摘要
研究旋转球形壳中混沌热对流的自我维持的磁场产生的螺旋性和跨热性电动发电机的相对重要性作为壳厚度的函数。发现在直接数值模拟中，针对0.25和0.6之间的直接数值模拟共存两个不同的分支 - 平均场偶极状态和波动的偶极状态。比较和对比表征共存的发电机吸引子的性能，包括磁场和旋转热对流的时间行为和空间结构的差异。发现在波动的偶性发电机状态下，螺旋性$α$效应和交叉效果$γ$效应的强度可比，在壳厚度上，它们的比率并没有很大差异。相比之下，在平均场偶极发电机状态下，螺旋性$α$效应占主导地位大约两个数量级，并且随着壳厚度的减小而变得更强大。
The relative importance of the helicity and cross-helicity electromotive dynamo effects for self-sustained magnetic field generation by chaotic thermal convection in rotating spherical shells is investigated as a function of shell thickness. Two distinct branches of dynamo solutions are found to coexist in direct numerical simulations for shell aspect ratios between 0.25 and 0.6 - a mean-field dipolar regime and a fluctuating dipolar regime. The properties characterising the coexisting dynamo attractors are compared and contrasted, including differences in temporal behavior and spatial structures of both the magnetic field and rotating thermal convection. The helicity $α$-effect and the cross-helicity $γ$-effect are found to be comparable in intensity within the fluctuating dipolar dynamo regime, where their ratio does not vary significantly with the shell thickness. In contrast, within the mean-field dipolar dynamo regime the helicity $α$-effect dominates by approximately two orders of magnitude and becomes stronger with decreasing shell thickness.
