CAREER: Understanding and Modeling the Mysterious Dropout of Radiation Belt Electrons

这个项目的重点是对地球辐射带中的相对论电子布居动力学进行建模。如果不完全了解电子的神秘丢失，就不可能完全理解和预测辐射带的动力学。鉴于对空间系统的危害，这一点具有相当重要的实际意义。许多通信卫星和国家安全资产驻留在这种辐射环境中，它们的寿命取决于其动态。科学的进步支持预测模型的改进，并直接符合2015年发布的国家空间天气战略和行动计划的目标。该项目支持一名女教员，并将在研究和外联活动中对研究生和本科生进行培训和教育。学习单元将为西弗吉尼亚州的K-12学校提供前所未有的空间科学非正式学习机会。预计将提高中学生对该州STEM项目的认识和兴趣，并激励他们追求STEM职业生涯，特别是代表不足的女性和社会经济地位较低的学生。开发和提供学习模块的机会还将为本科生和研究生提供宝贵的教育和外展经验，并提高他们的科学素养和沟通技能。自2012年美国国家航空航天局范艾伦探测器发射以来，在理解相对论电子的强劲增强方面取得了重大进展。然而，辐射带电子的快速和戏剧性的丢失(几个小时内就有几个数量级)仍然没有解决。存在一个悬而未决的问题：在退学期间，电子去了哪里？该奖项旨在开发一种新的全面的辍学模型，名为相对论电子辍学(RED)，该模型具有物理和特定于事件的输入，以模拟电子辍学并了解管理过程。RED将不仅包括传统的损失过程(俯仰角扩散、磁层顶阴影和向外径向扩散)，而且还包括被称为漂移轨道分叉(道布)的新机制。这些过程的物理量化将基于真实的场和粒子条件来实现。有了这些输入，RED将模拟在高海拔观测到的电子丢失和在低海拔观测到的电子沉淀，以解决控制机制。来自Van Allen探测器、THEMIS和MMS航天器的丰富的高能电子和波测量覆盖了从外带到磁层顶的区域，以及低海拔的多颗POES卫星，将为红色模型提供一个很好的测试基础。这一模式将第一次纳入辍学期间的所有主要损失机制，包括新的道布进程。它既能模拟高海拔地区的电子丢失，又能模拟低海拔地区的降水，这将对理解降水过程中的支配过程和解决它们的相对重要性做出重要贡献。对磁层顶阴影、道布和径向扩散过程的物理和特定事件的量化对于理解快速电子丢失以及整个辐射带动态是新的和关键的。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project focuses modeling of the relativistic electron population dynamics in Earth's Radiation Belts. Without fully understanding the mysterious dropout of electrons, a full understanding and prediction of radiation belt dynamics cannot be reached. This is of considerable practical importance due to the hazards to space-borne systems. Many communications satellites and national security assets reside in this radiation environment and their lifetime depends on its dynamics. Advancing the science supports improvement of the predictive models and fits directly into the goals of the National Space Weather Strategy and Action Plan, which was released in 2015. The project supports a female faculty member and will train and educate graduate and undergraduate students in both research and outreach activities. The learning module will provide an unprecedented informal learning opportunity on space science to West Virginia K-12 schools. It is expected to increase the awareness and interest of middle school students in the STEM programs in the state, and inspire them to pursue STEM careers, especially the underrepresented female and lower socioeconomic status students. The opportunities to develop and deliver the learning module will also provide valuable educational and outreach experience for undergraduate and graduate students and enhance their science literacy and communication skills.Since the launch of NASA Van Allen Probes in 2012, significant progress has been achieved in understanding the strong enhancement of relativistic electrons. However, the fast and dramatic dropout of radiation belt electrons (orders of magnitudes in a few hours) remains unsolved. The open question exists: Where do the electrons go during the dropout? This award is to develop a new and comprehensive dropout model, named Relativistic Electron Dropout (RED), with physical and event-specific inputs to simulate the electron dropout and understand the governing processes. RED will include not only the traditional loss processes (pitch angle diffusion, magnetopause shadowing, and outward radial diffusion), but also the new mechanism called Drift Orbit Bifurcation (DOB). Physical quantification of these processes will be achieved based on realistic field and particle conditions. With these inputs, RED will simulate both the electron dropout observed at high altitudes and the electron precipitation observed at low altitudes to resolve the governing mechanisms. The wealth of energetic electron and wave measurements from Van Allen Probes, THEMIS, and MMS spacecraft that cover the region from the outer belt to the magnetopause and the multiple POES satellites at low altitudes will provide an excellent test base for the RED model. This model will be the first to incorporate all the major loss mechanisms during the dropout, including the new DOB process. It is capable of simulating both electron dropout at high altitudes and precipitation at low altitudes, which will make a significant contribution in understanding the governing processes during the dropout and resolving their relative importance. The physical and event-specific quantification of the magnetopause shadowing, DOB, and radial diffusion processes is new and critical for understanding the fast electron dropout as well as the overall radiation belt dynamics.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.