PREEVENTS Track 2: Integrated Modeling of Extreme Space Weather Events from Electron to Global Scales

空间天气是由太阳活动引起的，它会影响地球的空间环境，破坏我们的技术系统，并使飞行员和宇航员暴露在有害的辐射中。极端的太空天气事件是由磁重联引起的磁层的突然重构引起的，磁重联是围绕和保护地球的磁场，可以被认为是磁爆炸。重联发生在比磁层小得多的尺度上。该项目将利用复杂的计算机模型预测极端太空天气事件的影响。利用创新的算法和最先进的模型，该项目将实现对极端空间天气事件的首次自一致的全球模拟，从而捕捉到重连的物理现象。极端的太空天气事件可能会破坏地球上的电网，需要几个月的恢复时间，并在很长一段时间内造成大规模的电力损失，并可能使我们的技术基础设施崩溃。该项目的结果将允许对各种影响进行定量评估，这是预防计划和工程解决方案所需要的。本项目支持培养多名研究生。目前的磁层模型，包括正在过渡到NOAA空间天气模拟中心运行的密歇根地球空间模型，采用的磁流体动力学（MHD）近似不能解释导致磁重联的动力学过程。只有第一性原理的、完全动态的代码才能可靠地模拟重连接，但在当前或不久的将来的计算机上，全球动态模拟是负担不起的。最近开发的MHD与嵌入颗粒细胞（MHD- epic）算法提供了一个独特的解决方案。MHD代码提供了全计算域的全局解决方案，而全动力学EPIC代码则对发生重连的部分区域进行建模。MHD-EPIC比全局动力学模型更有效，这项技术已经成功地在几个空间物理系统中得到验证，包括木卫三、水星、火星和地球的磁层。MHD-EPIC模式将用于研究极端空间天气事件。首先，该模型将根据观测到的强磁暴进行验证。然后，经过验证的模型将被用来模拟如果2012年7月卡灵顿规模的太阳喷发没有错过地球会发生什么。将对理想化和放大的真实事件进行建模，以研究各种情景：极端太阳风冲击压力、磁场、持续时间和变异性。对于每一次运行，将计算局部表面磁场的变化，并作为基于物理的电网模型的输入。

Space weather results from solar activity that can affect the space environment of Earth, damage our technological systems, and expose pilots and astronauts to harmful radiation. Extreme space weather events are caused by sudden reconfigurations of the magnetosphere, the magnetic field surrounding and protecting Earth, caused by magnetic reconnection, which can be thought of as a magnetic explosion. Reconnection happens on scales much smaller than the magnetosphere. The project will predict the effects of extreme space weather events with a sophisticated computer model. Using innovative algorithms and state-of-the-art models, the project will realize the first-ever self-consistent global simulations of extreme space weather events that capture the physics of reconnection. Extreme space weather events could knock out the power grid on Earth with a recovery time of months and the large-scale loss of electricity for an extended time and could collapse our technological infrastructure. The results of this project will allow quantitative assessment of the various impacts, which is needed for prevention plans and engineering solutions. This project supports the training of multiple graduate students.Current magnetosphere models, including the Michigan Geospace model being transitioned to operation at the Space Weather Modeling Center of NOAA, employ a magnetohydrodynamic (MHD) approximation that cannot account for the kinetic processes responsible for magnetic reconnection. Only first-principles, fully kinetic codes can reliably model reconnection, but global kinetic simulations are not affordable on current or even near-future computers. The recently developed MHD with embedded particle-in-cell (MHD-EPIC) algorithm offers a unique solution. The MHD code provides the global solution in the full computational domain, while the fully kinetic EPIC code models the parts of the domain where reconnection occurs. MHD-EPIC is much more efficient than a global kinetic model and this technique has been successfully validated for several space physics systems, including the magnetospheres of Ganymede, Mercury, Mars and Earth. The MHD-EPIC model will be employed to study extreme space weather events. First the model will be validated against observations for well-observed strong magnetic storms. Then the validated model will be used to simulate what would have happened if the July 2012 Carrington-scale solar eruption had not missed Earth. Idealized and scaled-up real events will be modeled to investigate various scenarios: extreme solar wind ram pressure, magnetic field, duration, and variability. For each run the local surface magnetic field variations will be calculated and serve as input for physics-based models of power grids.