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

NSWP：地球空间天气中的因果电子降水：模型开发、验证、事件研究

• 批准号: 1023346
• 负责人: William Lotko
• 金额: $ 30.7万
• 依托单位: Dartmouth College
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-08-15 至 2014-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1023346&HistoricalAwards=false
• 关键词: NSWP; Causal; Electron; Precipitation; Geospace

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.

该项目的动机是一个重要问题：电子降水的区域和全球特征的时空变异性如何影响磁层-电离层(MI)相互作用？电子从磁层向电离层的沉淀改变了电离层的电学性质。通过改变电离层的电导和尺度高度，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向空间的引力逃逸方面发挥了主要作用。因此，电子降水的通量分布和半球功率等特征被认为是空间天气预报的关键变量。目前对电子沉淀影响的了解主要来自基于指数的非因果经验降水模型和嵌入磁层全球模拟的简单第一原理模型。这两种方法都没有充分捕捉到在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。该项目在推动最先进技术方面迈出了重要的一步，开发了物理上真实的电子沉淀模型，该模型可以由来自磁层的全球磁流体动力学(MHD)模拟的状态变量进行因果调节。主要的科学目标是：i)提高在地球空间环境的数值模拟中预测的电子降水通量的保真度，以及ii)利用模拟来研究电子降水对MI相互作用的影响。预期的创新包括改进直接入射、扩散和单能降水的规范，以及开发新的二次和宽带降水模式。将在Lyon-Fedder-Mobarry(LFM)全球模拟模型的独立版本以及合并LFM模型和热层-电离层-热层电动力学一般环流模型(TIEGCM)的磁层-电离层-热层耦合模型(CMIT)的背景下测试拟议的开发并校准其准确性。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区电离的分布和动力学以及由此产生的电导率的影响。该项目通过促进发现和理解，将研究和教育结合起来，同时促进一名博士生的教学和专业发展，该博士生将在首席研究员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的参与科学家和国家大气研究中心之间的伙伴关系来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：可在任何全球磁层磁流体力学模拟模型中实施的创新的降水模式；通过提高我们预报地球空间天气的能力而造福社会；对物理属性和地球空间电子降水影响之间因果关系的更深入的科学理解。