Collaborative Research: GEM--How Upstream Solar Wind Conditions Determine the Properties of the Foreshock Backstreaming Ions

合作研究：GEM——上游太阳风条件如何决定前震回流离子的特性

• 批准号: 2247758
• 负责人: Kun Zhang
• 金额: $ 27.11万
• 依托单位: SPACE SCIENCE INSTITUTE
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-08-15 至 2024-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2247758&HistoricalAwards=false
• 关键词: Collaborative; Research; GEM; How; Upstream

The interaction of the solar wind and the Earth's magnetic field created a collisionless shock called a bow shock in front of the Earth's magnetosphere. The incident particles can be accelerated and reflected at the bow shock, resulting in their counter-streaming along field lines and interacting with the local plasma. Earth's bow shock is a natural laboratory to study the complex interactions between the incident solar wind and the counter-streaming foreshock populations. This study aims to build a predictive model of the foreshock backstreaming ions, which can be integrated into a space weather prediction model to help accurately forecast and mitigate space weather hazards. An early-career female scientist leads this project and involves the participation of multiple early-career scientists. The related science materials will be presented to k-12 students, parents, and the general public audience through various outreach events to promote STEM education.This study focuses on the foreshock ion properties and addresses the following questions: (1) What are the properties of the freshly reflected ions near the bow shock, including reflection rate, velocity, perpendicular and parallel temperatures and Velocity Distribution Function (VDF) types (e.g., field-aligned beam, ring distributions, etc), as a function of upstream solar wind conditions (e.g., speed, interplanetary magnetic field (IMF), Mach number, beta, etc) and shock normal angles? (2) How do the properties of the freshly reflected ions evolve spatially and temporally as they travel away from the bow shock as suggested by global simulations? (3) Can the obtained properties be explained by existing acceleration and reflection theories, such as adiabatic and specular reflections? The project combines analysis of satellite measurements and numerical simulations to reveal how the ion distributions are determined by the upstream solar wind conditions. This project will improve our understanding of the properties of the bow shock reflected ions and the related reflection, acceleration, and scattering processes.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.

太阳风和地球磁场的相互作用在地球磁层前面产生了一种称为弓形激波的无碰撞激波。 入射粒子可以在弓激波处加速和反射，导致它们沿着场线逆流并与局部等离子体相互作用。 地球的弓形激波是研究入射太阳风和逆流前震群之间复杂相互作用的天然实验室。 本研究旨在建立前震回流离子的预测模型，该模型可以集成到空间天气预测模型中，以帮助准确预测和减轻空间天气灾害。 一位早期职业女性科学家领导该项目，并有多名早期职业科学家参与。 相关科普材料将通过各种外展活动向k-12学生、家长和广大公众展示，以促进STEM教育。本研究重点关注前震离子特性并解决以下问题：（1）什么是特性弓激波附近新反射离子的数量，包括反射率、速度、垂直和平行温度以及速度分布函数 (VDF) 类型（例如场对准光束、环分布等），作为上游太阳风条件的函数（例如速度、行星际磁场 (IMF)、马赫数、β 等）和激波法线角？ (2) 如全局模拟所示，当新反射的离子远离弓激波时，它们的特性如何在空间和时间上演变？ (3) 所获得的性质可以用现有的加速和反射理论（例如绝热反射和镜面反射）来解释吗？ 该项目结合了卫星测量和数值模拟的分析，以揭示离子分布如何由上游太阳风条件决定。 该项目将提高我们对弓形激波反射离子的特性以及相关反射、加速和散射过程的理解。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点和更广泛的影响审查进行评估，被认为值得支持标准。