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

太阳风和地球磁场的相互作用在地球磁层前产生了一种称为弓形激波的无碰撞激波。入射粒子在弓形激波处被加速和反射，导致它们沿场线逆流，并与局部等离子体相互作用。地球弓形激波是研究入射太阳风与反流前激波群之间复杂相互作用的天然实验室。本研究旨在建立前震逆流离子的预测模型，将其整合到空间天气预报模型中，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这个项目，并涉及多个早期职业科学家的参与。相关科学材料将通过各种外展活动向k-12学生、家长和公众展示，以推广STEM教育。本研究的重点是前激波离子的特性，并解决以下问题：(1)在弓形激波附近新反射离子的特性是什么，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（如场向束、环分布等），作为上游太阳风条件（如速度、行星际磁场（IMF）、马赫数、β等）和激波法线角的函数？(2)根据全局模拟，新反射的离子在远离弓形激波的过程中，其特性在空间和时间上是如何演变的？(3)所得性质是否可以用现有的加速和反射理论（如绝热反射和镜面反射）来解释？该项目结合了卫星测量和数值模拟的分析，揭示了离子分布是如何由上游太阳风条件决定的。这个项目将提高我们对弓形激波反射离子的特性以及相关的反射、加速和散射过程的理解。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知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.