Interior Structure and Dynamics of the Ice Giants

冰巨星天王星和海王星提供了几个有趣的谜题。它们的磁场与其他行星不同，因为它们不是由偶极分量主导的，并且具有非常复杂的结构，没有任何明显的对称性。此外，虽然冰巨星远离太阳，但它们的大气风是太阳系中最快的。另一个难题是天王星的光度太低。所有这些特征都为这些行星的特殊内部结构和动力学提供了线索，必须根据科学模型进行解释。然而，为了变得更有用，这些模型需要改进。我们计划集中在模型的内部动态和磁场产生在这个建议。有六种不同的方法可以解释为什么天王星和海王星的磁场不是偶极主导的。例如，密度分层或电导率的径向变化是两个可能的原因。几个建议的替代方案起源于我们的小组，我们有数字手段来进一步研究所有这些方案，以探索它们的潜力。为了更好地约束动力学模型，我们将与罗斯托克的罗纳德雷德默教授和利物浦的理查德霍姆教授周围的小组合作。罗斯托克小组将提供内部结构和材料特性的模型;理查德·霍姆教授拥有必要的专业知识，可以根据旅行者号的原始数据测试模拟磁场。有六种不同的场景来获得非偶极主导的场并不一定意味着所有这些场都是天王星或海王星。最终目标是构建一个模型，该模型符合我们对内部结构，磁场以及理想情况下观察到的表面风的知识。后一点涉及到这些猛烈的风是如何驱动的以及它们到达地球的深度。

The ice giants Uranus and Neptune offer several interesting puzzles. Their magnetic fields differ from those of any other planet since they are not dominated by a dipole component and have a very complex structure without any obvious symmetry. Moreover, though the ice giants are far away from the sun their atmospheric winds are the fastest in the solar system. Another puzzle is the fact that Uranus’ luminosity is too low. All these features offer clues about the special interior structure and dynamics of these planets that must be interpreted based on scientific models. To become more useful, however, these models need to be refined. We plan to concentrate on models concerning the interior dynamic and magnetic field generation in this proposal. Six different options have been suggested to explain why the magnetic fields of Uranus and Neptune are not dipole-dominated. For example, the density stratification or the radial variations in electrical conductivity are two possible reasons. Several of the suggested alternatives originated in our group and we have the numerical means to study all of them further in order to explore their potential. To better constrain the dynamical models we will collaborate with the group around Prof. Ronald Redmer in Rostock and around Prof. Richard Holme in Liverpool. The Rostock group will provide models of the interiors structure and material properties; Prof. Richard Holme has the expertise necessary to test the simulated magnetic fields against the original Voyager data. Having six different scenarios to obtain non dipole-dominated fields doesn’t necessarily mean that all these fields are Uranus or Neptune-like. The ultimate goal is to construct a model that is compliant with our knowledge of the interior structure, of the magnetic fields and ideally also with the observed surface winds. The latter point touches on the question how these fierce winds are driven and how deep they reach into the planet.