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首页> 外文期刊>Physics of the Earth and Planetary Interiors: A Journal Devoted to Obsevational and Experimerntal Studies of the Chemistry and Physics of Planetary Interiors and Their Theoretical Interpretation >Anelastic dynamo models with variable electrical conductivity: An application to gas giants
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Anelastic dynamo models with variable electrical conductivity: An application to gas giants

机译：具有可变电导率的非弹性发电机模型：在天然气巨头中的应用

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The observed surface dynamics of Jupiter and Saturn are dominated by a banded system of fierce zonal winds. The depth of these winds remains unclear but they are thought to be confined to the very outer envelopes where hydrogen remains molecular and the electrical conductivity is small. The dynamo maintaining the dipole-dominated magnetic fields of both gas giants, on the other hand, likely operates in the deeper interior where hydrogen assumes a metallic state.Here, we present numerical simulations that attempt to model both the zonal winds and the interior dynamo action in an integrated approach. Using the anelastic version of the MHD code MagIC, we explore the effects of density stratification and radial electrical conductivity variations. The electrical conductivity is mostly assumed to remain constant in the thicker inner metallic region and it decays exponentially towards the outer boundary throughout the molecular envelope.Our results show that the combination of a stronger density stratification and a weaker conducting outer layer is essential for reconciling dipole dominated dynamo action and a fierce equatorial zonal jet. Previous simulations with homogeneous electrical conductivity show that both are mutually exclusive, with solutions either having strong zonal winds and multipolar magnetic fields or weak zonal winds and dipole-dominated magnetic fields. All jets tend to be geostrophic and therefore reach right through the convective shell in our simulations.The particular setup explored here allows a strong equatorial jet to remain confined to the weaker conducting outer region where it does not interfere with the deeper seated dynamo action. The flanking mid to high latitude jets, on the other hand, have to remain faint to yield a strongly dipolar magnetic field. The fiercer jets on Jupiter and Saturn only seem compatible with the observed dipolar fields when they remain confined to a weaker conducting outer layer.
机译：观测到的木星和土星的表面动力学主要由强烈的纬向风带状系统控制。这些风的深度尚不清楚，但据认为仅限于最外面的外壳，在外壳中氢仍然是分子且电导率很小。另一方面，维持两个气体巨头的偶极子主导磁场的发电机很可能在更深的内部（氢呈金属态）运行。在这里，我们提供了数值模拟，试图模拟纬向风和内部发电机综合行动。使用MHD代码MagIC的非弹性版本，我们探索了密度分层和径向电导率变化的影响。通常认为电导率在较厚的内部金属区域中保持恒定，并且在整个分子包膜中朝着外边界呈指数衰减。我们的结果表明，较强的密度分层和较弱的导电外层的组合对于调和偶极子至关重要主导的发电机动作和猛烈的赤道纬向射流。以前具有均匀电导率的模拟表明，两者是互斥的，解决方案要么具有强的纬向风和多极磁场，要么具有弱的纬向风和偶极子主导的磁场。所有的射流都倾向于地转，因此在我们的模拟中将穿过对流壳。此处探索的特定设置使强的赤道射流保持在较弱的传导外部区域，在该区域不会干扰更深的发电机作用。另一方面，侧向的中高纬度射流必须保持微弱才能产生强的偶极磁场。当木星和土星上的更猛烈的射流保持在较弱的导电外层时，它们似乎只与观察到的偶极场兼容。

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