Convection and magnetic field generation in the Earth and planetary interiors are driven by both thermal and compositional gradients. In this work numerical simulations of finite-amplitude double-diffusive convection and dynamo action in rapidly rotating spherical shells full of incompressible two-component electrically-conducting fluid are reported. Four distinct regimes of rotating double-diffusive convection identified in a recent linear analysis (Silva, Mather and Simitev, Geophys. Astrophys. Fluid Dyn. 2019, 113, 377) are found to persist significantly beyond the onset of instability while their regime transitions remain abrupt. In the semi-convecting and the fingering regimes characteristic flow velocities are small compared to those in the thermally- and compositionally-dominated overturning regimes, while zonal flows remain weak in all regimes apart from the thermally-dominated one. Compositionally-dominated overturning convection exhibits significantly narrower azimuthal structures compared to all other regimes while differential rotation becomes the dominant flow component in the thermally-dominated case as driving is increased. Dynamo action occurs in all regimes apart from the regime of fingering convection. While dynamos persist in the semi-convective regime they are very much impaired by small flow intensities and very weak differential rotation in this regime which makes poloidal to toroidal field conversion problematic. The dynamos in the thermally-dominated regime include oscillating dipolar, quadrupolar and multipolar cases similar to the ones known from earlier parameter studies. Dynamos in the compositionally-dominated regime exhibit subdued temporal variation and remain predominantly dipolar due to weak zonal flow in this regime. These results significantly enhance our understanding of the primary drivers of planetary core flows and magnetic fields.

中文翻译：

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旋转球壳中的热成分对流和相关发电机的机制

地球和行星内部的对流和磁场产生是由热梯度和成分梯度驱动的。在这项工作中，报告了在充满不可压缩的双组分导电流体的快速旋转球壳中有限幅度双扩散对流和发电机作用的数值模拟。在最近的线性分析（Silva、Mather 和 Simitev, Geophys. Astrophys. Fluid Dyn. 2019, 113, 377）中发现的四种不同的旋转双扩散对流状态在不稳定开始后仍显着持续，而它们的状态转换仍然存在突然。在半对流和指法状态下，与热和成分主导的倾覆状态相比，特征流速小，而除了热主导的区域外，所有区域的纬向流仍然很弱。与所有其他状态相比，成分主导的翻转对流显示出明显更窄的方位角结构，而随着驱动的增加，差动旋转成为热主导情况下的主导流动分量。发电机作用发生在除指法对流机制之外的所有机制中。虽然发电机在半对流状态下持续存在，但它们在该状态下受到小流动强度和非常弱的微弱旋转的极大损害，这使得极向场到环形场的转换成为问题。热主导状态中的发电机包括振荡偶极、四极和多极情况，类似于早期参数研究中已知的情况。在成分占主导地位的区域中，发电机表现出柔和的时间变化，并且由于该区域中的纬向流动较弱，因此主要保持偶极。这些结果显着增强了我们对行星核心流动和磁场的主要驱动因素的理解。