论文标题
部分可观测时空混沌系统的无模型预测
Non-synchronous rotation on Europa driven by ocean currents
论文作者
论文摘要
有人建议，由于潮汐扭矩，木星月亮的冰壳可能会非同步漂移。在这里，我们认为，基础海洋施加的扭矩也很重要，并且可能导致非同步旋转（NSR）。所得的自旋速率可能比同步角度速率稍慢一些，而同步角速率将使冰壳面向木星的相同点。我们开发了一个冰壳旋转模型，该模型是由使用高分辨率的海洋一般循环模型计算出的海洋应力驱动的，并考虑了冰壳的粘弹性变形。我们使用冰壳模型的结果以及观察到的冰壳漂移速度的限制来限制冰壳参数，例如有效粘度，目前至少尚不确定至少四个数量级。我们的结果充其量表明，冰壳对流缓慢。根据冰壳的松弛时间尺度和洋流，冰壳可能会在随机波动上叠加时表现出微不足道的漂移，恒定漂移或振荡性漂移。预期旋转率超过$ \ sim $ 30〜m/yr；未来的航天器观测值可用于测试这些预测，并洞悉冰壳和下面海洋的性质。
It has been suggested that the ice shell of Jupiter's moon Europa may drift non-synchronously due to tidal torques. Here we argue that torques applied by the underlying ocean are also important and can result in non-synchronous rotation (NSR). The resulting spin rate can be slightly slower than the synchronous angular rate that would have kept the same point of the ice shell facing Jupiter. We develop an ice shell rotation model, driven by ocean stress calculated using a high-resolution state-of-the-art ocean general circulation model, and take into account the viscoelastic deformation of the ice shell. We use the ice shell model results together with observed limits on the ice shell drift speed to constrain ice shell parameters such as effective viscosity, which is currently uncertain by at least four orders of magnitude. Our results suggest, at best, sluggish ice shell convection. Depending on the relaxation time scale of the ice shell and on the ocean currents, the ice shell may exhibit negligible drift, constant drift, or oscillatory drift superimposed on random fluctuations. The expected rotation rate exceeds $\sim$30~m/yr; future spacecraft observations can be used to test these predictions and yield insight into the properties of the ice shell and underlying ocean.
