Towards realistic models for the interior dynamics of Jupiter and Saturn

大多数数值发电机代码都是在考虑地球发电机的情况下开发的。他们忽略了发电机介质的可压缩性，并且还假设发电机区域从上覆的电绝缘体（地球的情况下是岩石地幔）动态地扩展。这两个假设在地球发电机的背景下都是合理的，但在气体巨星木星和土星的内部却不是。在这里，密度随着深度显著增加。此外，这些行星的发电机区域并没有明显地与覆盖的气体包层分离，因为电导率随深度的增加是渐进的而不是突然的。另一个有趣的特征，迄今为止很少有人探索，是氦沉淀被认为至少发生在土星的外层。它实际上可能是行星特有磁场的原因。我们计划开发新的数值发电机模型，探索可压缩性的影响，氦雨，分子气体信封和更深的发电机区域之间的耦合。后者是计划于2011年发射的朱诺号木星任务的关键问题之一。我们的模拟将不仅支持这一使命，但也提供了现实的模型，土星的发电机的时间为第二次延长卡西尼号使命。

The majority of numerical dynamo codes where developed with the geodynamo in mind. They neglect the compressibility of the dynamo medium and also assume that the dynamo region dynamically decouples from an overlying electrically insulating body – the rocky mantle in the case of Earth. Both assumptions are justified in the geodynamo context but not for the interior of the gas giants Jupiter and Saturn. Here, the density increases significantly with depth. Also, the dynamo region of these planets is not clearly decoupled from the overlying gas envelope since the increase in electrical conductivity with depth is gradual rather than abrupt. Another interesting feature, which has little been explore so far, is the helium precipitation thought to happen at least in Saturn’s outer layers. It may actually be responsible for the planets peculiar magnetic field. We plan to develop new numerical dynamo models that explore the effects of compressibility, of helium-rain, and of the coupling between the molecular gas envelope and the deeper dynamo region. The latter is one of the key questions for the Juno missions to Jupiter scheduled to be launched in 2011. Our simulations will not only support this mission but also provide realistic models for Saturn’s dynamo in time for the second extended Cassini mission.