Exploring the Giant Planet Energy Crisis with JWST

木星、土星、天王星和海王星这些巨大的行星一直是令人敬畏和鼓舞的源泉。我们对这些系统的第一次近距离观察来自40多年前的早期宇宙飞船，如先驱者号和旅行者号，揭示了与地球完全不同的行星。这些巨大的致密气体球体显示出复杂而猛烈的云层结构，每颗行星的卫星数量都超过了太阳系中的行星数量。这些行星的上层大气层包含行星和周围空间环境之间的界面，带电粒子电离层是‘感觉’磁场的所有重要管道。这是一个关键区域，因为正是在这里，能量通过强大的极光过程进行交换，产生关于磁极的令人惊叹的光显示。通过地面观测，我们可以测量巨行星上层大气的全球温度，我们发现它们的温度比我们对该地区的模型预测的要高得多。这是一个几十年前的重大行星科学悬而未决的问题，被戏剧性地命名为“能源危机”。对于这个令人困惑的问题，已经提出了两种解决方案。首先，极光可以在两极注入大量的能量，但由于这些行星绕轴自转的速度比地球快得多，似乎有一些力阻止了这些能量向赤道方向移动。其次，我们在这些行星的图像中看到的戏剧性湍流会产生波，这些波可以在高度上传播，并在高层大气中破裂和释放能量，在这个过程中加热它。到目前为止，我们还没有测试这些理论和解决这场危机所需的高保真数据。这就是这个奖学金计划要做的事情。詹姆斯·韦伯太空望远镜(JWST)是美国、欧洲和加拿大太空机构合作的产物，是有史以来建造的最强大的望远镜，将于2021年10月从法属圭亚那搭载欧洲火箭发射。由于望远镜位于远离地球大气层的深空，而且仪器极其灵敏，该设施将提供从我们自己的太阳系到非常早期的宇宙的全新视角。JWST已经计划了一些观测，其中包括我密切参与开发的对木星和天王星的观测。这将不同于地球上的地面望远镜所能实现的任何目标，将提供这些行星大气层令人难以置信的详细视图，并提供一个一劳永逸地解决能源危机的机会。这项研究计划将使用JWST的两台仪器--由莱斯特大学大力参与的英国建造的中红外仪器(MIRI)和由欧洲航天局领导的近红外光谱仪(NIRSpec)。通过将这两台仪器的数据结合起来，我们可以捕捉到整个大气层的光线，从大气的深层湍流基础，一直到高层大气和电离层。对这些数据的分析将揭示能量是如何在大气层内部和之间传输的，我将直接测试针对能源危机提出的两种解决方案。通过观察木星和天王星的大气层，我们得到了气体巨星和冰巨星的能量传输的观点，这两个不同类别的行星可能确实为危机提供了两种不同的解决方案。在太阳系外发现的大多数行星与木星和天王星都有许多共同的特征，应用我们从这个计划中学到的东西可以大大加深我们对围绕其他恒星运行的行星的理解。

The giant planets, Jupiter, Saturn, Uranus, and Neptune, have always provided a source of both awe and inspiration. Our first close-up glimpses of these systems came from early spacecrafts such as the Pioneers and the Voyagers over 40 years ago, revealing planets that were positively nothing like the Earth. These great spheres of dense gas showed intricate and violent cloud structures, with each planet having more moons than there are planets in the solar system. The upper atmosphere of these planets contain the interface between the planet and the surrounding space environment, with the charged particle ionosphere being the all important conduit that 'feels' the magnetic field. This is a critical region, because it is here that energy is exchanged via the powerful auroral process, producing stunning displays of light about the magnetic poles. From ground-based observations we can measure the global temperature of the upper atmosphere of the giant planets, and we find that they are much hotter than our models of this region predict. This is a decades-old and a major outstanding question in planetary science and has been dramatically named the 'energy crisis'. Two solutions to this puzzling problem have been proposed. Firstly the aurora can inject significant amounts of energy at the poles, but since these planets are spinning on their axis much faster than the Earth, there are forces that appear to prohibit the movement of this energy down towards the equator. Secondly, the dramatic turbulence that we see in images of theses planets generate waves that can travel up in altitude and break and release their energy in the upper atmosphere, heating it in the process. Up until now, we have not had the high fidelity data needed to test these theories, and to solve this crisis. This is what this Fellowship programme sets out to do. The James Webb Space Telescope (JWST), a collaboration between American, European, and Canadian space-agencies, is the most powerful telescope ever constructed, and it will be launched from French Guiana on a European rocket in October 2021. Since the telescope is situated in deep space, far away from the Earth's atmosphere, and because the instruments are incredibly sensitive, the facility will provide completely new views of the universe, from our own solar system to the very early universe. A number of observations have already been planned with JWST, and those include observations of Jupiter and Uranus that I have closely been involved in the development of. These will be unlike anything achievable with telescopes on the ground at Earth, and will provide an incredibly detailed view of the atmospheres of these planets, and an opportunity to once and for all address the energy crisis. This research programme will use two of JWST's instruments - the Mid Infrared Instrument (MIRI), build in the UK with significant involvement by the University of Leicester, and the Near-Infrared Spectrograph (NIRSpec), led by the European Space Agency. By combining data from both instruments, we can capture light from the entire atmosphere, from the deep turbulent base of the atmosphere, all the way up to the upper atmosphere and the ionosphere. The analysis of these data will reveal how energy is transported within and between atmospheric layers, and I will directly test the two proposed solutions to the energy crisis. By observing the atmospheres of both Jupiter and Uranus, we get views of energy transport at both a Gas Giant and an Ice Giant, two different classes of planet that may indeed offer two different solutions to the crisis. Most of the planets discovered outside our solar system share many characteristics with either Jupiter and Uranus, and applying what we learn from this programme can significantly further our understanding of planets orbiting other stars.