Understanding Jupiter's polar vortex crystals, Mathematics

在包括地球在内的大多数太阳系行星的大气层中，极地涡旋是以极地上方或附近为中心的孤立的单个气旋。相比之下，木星的极地涡旋具有前所未有的结构，正如美国宇航局的朱诺号探测器最近发现的那样，每个极地上都有一个单一的气旋，周围有几个其他的气旋以晶体模式[1]。这些晶体结构，以及它们如何随时间变化[2]，在被观察之前没有被预测，解释它们形成和演化的机制仍然未知。一种可能的机制是潮湿对流（由于水凝结释放的潜热）在极地地区产生小涡旋，然后气旋通过“β漂移”机制向极地迁移并合并[3]。但是包括这些过程的模型在木星的极地地区发现了混乱移动的漩涡的随机场，而不是观察到的有序的漩涡晶体[4，5]。该项目的目的是确定不同的过程如何有助于将木星的两极从混乱的漩涡海洋转变为观测到的极涡的晶体秩序。我们建议使用几个数值模型来研究大气流体动力学和其他物理过程的相互作用如何使木星的极地区域有序。使用的模型从简单的浅水模型到最先进的木星大气环流模型（GCM）。这些模型中的每一个都是使用在埃克塞特开发的"Isca"建模框架构建的[6]。在这个项目中使用Isca的优点是可以打开和关闭不同的过程（例如潮湿对流），以测试每个过程所扮演的角色。在成功学生兴趣的指导下，将对每个模型进行实验，以了解这种晶体结构的漩涡是如何形成的，它们是如何维持的，以及它们在朱诺号使命的剩余时间内如何变化。[1]Adriani et al，Nature，555，2018，[2] Agle et al，https：//go.nasa.gov/2sgvwCc，2019，[3] Thomson and McIntyre，JAS 73，2016，[4]奥尼尔et al，Nature Geoscience 8，2015，[5] Brueshaber et al，Icarus 323，2019，[6] Thomson and Vallis，Atmosphere，10（12），803，2019.

Project DescriptionIn the atmospheres of most solar-system planets, including Earth, polar vortices are isolated single cyclones centred over or near the poles. By contrast, Jupiter's polar vortices have an unprecedented structure, as recently discovered by NASA's Juno probe, having a single cyclone over each pole surrounded by several other cyclones in crystalline patterns [1]. These crystalline structures, and how they change in time [2], were not predicted prior to being observed, and the mechanisms explaining their formation and evolution remain unknown. One possible mechanism is that moist convection (due to latent heat release from water condensation) produces small vortices in the polar regions, with the cyclones then migrating polewards via the 'beta-drift' mechanism and merging [3]. But models including these processes find random fields of chaotically-moving vortices in Jupiter's polar regions, rather than the orderly vortex crystals that are observed [4, 5]. This project's aim is to determine how different processes contribute to transforming Jupiter's poles from a sea of chaotic vortices to the crystalline order of the observed polar vortices.We propose to use several numerical models to study how order the interaction of atmospheric fluid dynamics and other physical processes can bring order to Jupiter's polar regions. The models to be used range from a simple shallow-water model through to a state-of-the-art General Circulation Model (GCM) configured for Jupiter. Each of these models has been built using the 'Isca' modelling framework, developed at Exeter [6]. The advantage of using Isca for this project is that different processes can be turned on and off (e.g. moist convection) to test the role each process plays. Guided by the interests of the successful student, experiments will be conducted with each of the models to understand how such crystalline arrangements of vortices can be formed, how they are sustained, and how they may change over the remaining length of the Juno mission.[1] Adriani et al, Nature, 555, 2018, [2] Agle et al, https://go.nasa.gov/2sgvwCc, 2019, [3] Thomson and McIntyre, JAS 73, 2016, [4] O'Neill et al, Nature Geoscience 8, 2015, [5] Brueshaber et al, Icarus 323, 2019, [6] Thomson and Vallis, Atmosphere, 10(12), 803, 2019.