论文标题
旋转球形壳的热组合对流和相关发电机的制度
Regimes of thermo-compositional convection and related dynamos in rotating spherical shells
论文作者
论文摘要
地球和行星内部的对流和磁场产生均由热和组成梯度驱动。在这项工作中，据报道，有限振幅的双扩散对流和发电机作用在迅速旋转的球形壳中，充满了不可压缩的两组式电导流体。在最近的线性分析中确定的旋转双扩散对流的四个不同的方案（Silva等，2019，Geophys。Astrophys。Fluiddyn。，doi：10.1080/03091929.2019.1640875）被发现持续了很大的持久性，而其状态仍然存在。与热和组成主导的倾覆方案相比，在半分转交和指法状态的特征流速度相比小，而除热为主导的方案以外，在所有方案中，Zonal流仍然较弱。与所有其他机制相比，以组成为主的倾覆对流表现出明显较窄的方位角结构，而随着驾驶的增加，差异旋转成为热为主导的情况下的主要流量成分。除指法对流的政权外，发电机动作发生在所有政权中。虽然Dynamos持续存在于半传染性方案中，但在这种状态下，它们会受到小流量强度和非常弱的差异旋转的极大损害，这使得与环形场磁场转化有关。热为主导的状态中的发电机包括振荡偶极，四极和多极的振荡，类似于从早期参数研究中知道的振荡偶极病例。由组成型制度中的发电机表现出柔和的时间变化，并且由于该方案中的纬向流量弱而主要保持偶极。这些结果显着增强了我们对行星核心流和磁场的主要驱动因素的理解。
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 et al., 2019, Geophys. Astrophys. Fluid Dyn., doi:10.1080/03091929.2019.1640875) 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.
