NSWP: Causal Electron Precipitation in Geospace Weather: Model Development, Validation, Event Studies

这个项目的动机是首要的问题：如何时空变化的区域和全球的电子沉淀的特点影响磁层电离层（MI）的相互作用？ 从磁层到电离层的电子沉淀改变了电离层的电特性。 通过改变电离层的电导率以及标度高度，电子沉淀在调节磁层-电离层耦合的电动力学以及电离层离子进入太空的引力逃逸方面起着主要作用。由于这些原因，电子降水的特征，如其通量分布和半球功率，被认为是空间天气预报的关键变量。目前对电子沉淀效应的理解主要来自基于指数的非因果经验沉淀模型和嵌入全球磁层模拟的简单第一原理模型。这两种方法都不能充分捕捉磁暴等重大空间天气事件期间发生的电子沉淀的复杂性或可变性。该项目通过开发物理上真实的电子沉淀模型，在推进最先进技术方面迈出了重要一步，该模型可以通过磁层全球磁流体动力学模拟得出的状态变量进行因果调节。主要的科学目标是：i）提高地球空间环境数值模拟中预测的电子沉淀通量的保真度; ii）利用模拟研究电子沉淀对MI相互作用的影响。预期的创新包括改进直接进入、扩散和单能降水的规格，以及开发二次和宽带降水的新模型。将在Lyon-Fedder-Mobarry（LFM）全球模拟模型以及磁层-电离层-热层耦合模型（CMIT）的独立版本的背景下测试拟议的发展，并校准其准确性，CMIT模型合并了LFM模型和热层-电离层电动力学大气环流模型（TIEGCM）。LFM模型将用于研究降水、场向电流、对流和焦耳耗散; TIEGCM将用于研究降水对E区和F区电离分布和动态的影响以及由此产生的电导率。该项目通过推进发现和理解来整合研究和教育，同时促进博士生的教学和专业发展，该博士生将在主要研究者及其合作者的指导下进行大部分研究。该项目将通过促进达特茅斯学院和国家大气研究中心的参与科学家之间的伙伴关系，加强研究和教育的基础设施。项目成果将在公共论坛、经评审的期刊出版物和会议报告中传播。遗产包括创新的降水模型，可以在任何全球磁流体模拟模型的磁层;造福社会，提高我们的预测地球空间天气的能力;和更深入的科学理解之间的因果关系的物理属性和电子降水在地球空间的影响。

This project is motivated by the overarching question: How does spatiotemporal variability in regional and global characteristics of electron precipitation influence the magnetosphere-ionosphere (MI) interaction? The precipitation of electrons from the magnetosphere into the ionosphere alters the electrical properties of the ionosphere. By altering the electrical conductance of the ionosphere as well as the scale height, electron precipitation plays a primary agent in regulating both the electrodynamics of magnetosphere-ionosphere coupling, but also the gravitational escape of ionospheric ions into space. For these reasons, characteristics of electron precipitation such as its flux distributions and its hemispheric power are recognized as key variables for space weather prediction. Current understanding of the effects of electron precipitation has been derived largely from index-based, non-causal empirical precipitation models and from simple first-principles models embedded in global simulations of the magnetosphere. Neither approach adequately captures the complexity or variability of electron precipitation that occurs during major space weather events such as magnetic storms. This project takes a major step in advancing the state-of-the-art by developing physically realistic electron precipitation models that can be causally regulated by state variables derived from global magnetohydrodynamic (MHD) simulations of the magnetosphere. The principal science objectives are i) to improve the fidelity of the electron precipitation fluxes predicted in numerical simulations of the geospace environment, and ii) to use the simulations to investigate the effects of electron precipitation on the MI interaction. Anticipated innovations include improvements in the specification of direct-entry, diffuse and monoenergetic precipitation and development of new models for secondary and broadband precipitation. The proposed developments will be will be tested and their accuracy calibrated in the context of a standalone version of the Lyon-Fedder-Mobarry (LFM) global simulation model as well as the coupled magnetosphere- ionosphere-thermosphere (CMIT) model, which merges the LFM model and the thermosphere-ionosphere electrodynamics general circulation model (TIEGCM). The LFM model will be used to study precipitation, field-aligned currents, convection, and joule dissipation; the TIEGCM will be used to study the impacts of precipitation on the distribution and dynamics of E- and F-region ionization and the resulting electrical conductivities. The project integrates research and education by advancing discovery and understanding while promoting the teaching and professional development of a PhD student who will perform the bulk of the research under the mentorship of the principal investigator and his collaborators. The project will enhance the infrastructure for research and education by fostering a partnership between participating scientists at Dartmouth College and the National Center for Atmospheric Research. Project results will be disseminated in public forums, in refereed journal publications and in conference presentations. Legacies include innovative precipitation models that can be implemented in any global MHD simulation model of the magnetosphere; benefit to society by advancing our capability to forecast geospace weather; and a deeper scientific understanding of causal relationships between the physical attributes and the impacts of electron precipitation in geospace.