EAGER: Transformative Modeling Studies of Magnetosphere-Ionosphere/Thermosphere System

地球周围的空间环境是非常动态的，对来自太阳的不断变化的等离子体和电磁场做出快速反应。太空中的风暴可以爆炸性地触发(如地震和火山)，在高层大气中驱动强电流，在固体地球中感应电流，从而扰乱电网；在电离层嵌入式层内重新分配带电粒子，这可能会干扰GPS导航系统；以及加热高层大气，从而增加阻力，从而降低卫星的轨道。高海拔地球空间环境的全球模型本质上是电磁的，可以跟踪地球周围磁场和电流的这些快速变化，而不是磁耦合的低海拔电离层/上层大气的模型，它们本质上是静电的。这项提议的重点是开发首个全球电离层/高层大气系统电磁模式，如果成功，该模式最终将纳入下一代空间气象模式。这个项目很适合热切的项目。风险很高，但如果它成功了，回报是新一代全球磁层-电离层模型，它可能会改变人们对快速发生扰动期间空间和高层大气之间耦合的一些最基本方面的看法，并可能通过提供对其他影响的预测来在观测中寻找新的发现。这些结果将最终提高空间天气预报的能力，并可能对行星大气、吸积盘、星云和星际介质的研究感兴趣。对马萨诸塞大学洛厄尔分校的一名研究生进行这项赠款的培训是向下一代空间科学家传授关于这一复杂数值方法的知识的极好手段，而且在短期内会产生更广泛的影响。目前的电离层-热层模型假定靠近地球的磁场是恒定的。但是，除非通过电离层闭合的电流产生的磁场的变化是自洽的，否则不能正确地表示像爆炸极光活动这样的快速时间尺度过程。使用目前的显式数值算法开发这样的模型的主要障碍已经是保持解的稳定性所需的难以处理的短时间步长(在100公里高度时短到百万分之一秒)，这决定了不切实际的长计算机运行时间以跟随系统的演变。PI正在实施地球航天界并不广为人知的新数值技术，该技术基于隐式算法，可以使用更长的时间步长，并优化模型以在高性能计算机上运行。然后，新的电磁模型将用于一些数值实验，以探索地球空间-高层大气耦合系统中快速发展的扰动的有争议的特征。

The space environment surrounding the Earth is extremely dynamic, responding rapidly to the changing plasma and electromagnetic fields arriving from the Sun. Storms in space can trigger explosively (like earthquakes and volcanoes), driving strong electric currents through the upper atmosphere, which induce currents in the solid earth that can disrupt power grids; redistributing the charged particles within the embedded layers of the ionosphere, which can interfere with GPS navigation systems; and heating the upper atmosphere, which increases drag degrading the orbits of satellites. Global models of the high-altitude geospace environment are electromagnetic in nature and can follow these rapid changes in the magnetic fields and currents surrounding Earth, not so models of the magnetically coupled lower altitude ionosphere/upper atmosphere, which are electrostatic in nature. This proposal is focused on the development of a first-of-its-kind global electromagnetic model of the ionosphere/upper atmosphere system that, if successful will ultimately be incorporated into next-generation space weather models. This project is appropriate for the EAGER program. It is high risk but the reward, if it succeeds, is a new generation of global magnetosphere-ionosphere models that could potentially change views on some of the most fundamental aspects of the coupling between space and the upper atmosphere during the rapid onset of disturbances and possibly trigger new discoveries by supplying predictions of other effects to search for in the observations. The results will ultimately improve capabilities for space weather prediction and are potentially of interest to the study of planetary atmospheres, accretion disks, nebula, and the interstellar medium. The training of a graduate student at the University of Massachusetts-Lowell on this grant is an excellent means of transferring knowledge about this complex numerical methodology to the next generation of space scientists and is a near-term broader impact.Present models of the ionosphere-thermosphere assume that the magnetic field close to Earth is constant. But fast time-scale processes like explosive auroral activity are not correctly represented unless the changes in the magnetic field produced by electric currents closing through the ionosphere are solved for self-consistently. A major impediment to developing such a model using present explicit numerical algorithms has been the intractably short time steps (as short as 1 millionth of a second at 100 kilometers altitude) required to maintain stability of the solution, which dictate unrealistically long computer run times in order to follow the evolution of the system. The PI is implementing new numerical technology not widely known in the geospace community based on implicit algorithms that enable the use of much longer time steps, and also optimizing the model to run on high-performance computers. The new electromagnetic model will then be used in a number of numerical experiments to explore controversial features of rapidly developing disturbances in the coupled geospace - upper atmosphere system.