GEM: Energy Conversion Associated with Non-equilibrium Velocity Distribution Functions in Dayside Magnetopause Reconnection

GEM：与日侧磁顶重联中非平衡速度分布函数相关的能量转换

• 批准号: 2247718
• 负责人: Haoming Liang
• 金额: $ 55.5万
• 依托单位: University of Maryland, College Park
• 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: 2023-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2247718&HistoricalAwards=false
• 关键词: GEM; Energy; Conversion; Associated; Non

Dayside magnetopause reconnection controls plasma and energy input into the magnetosphere from the solar wind. It is associated with significant plasma heating and particle acceleration, yet these processes are not well-understood. One reason is that energy conversion between work, internal energy, and heat is traditionally defined for Maxwellian distributions and measured with lower order moments of the velocity distribution function (VDF), but in collisionless plasmas, the VDFs frequently appear in a non-Maxwellian state. Such non-equilibrium distributions can be unstable to the generation of instabilities and plasma waves which affect the VDFs via self-consistent wave-particle interactions. This project investigates energy conversion associated with non-equilibrium VDFs, an important study for understanding and predicting space weather. The work supports an early career PI and a post-doc from an under-represented group in STEM. Undergraduate students will be mentored and outreach conducted through the annual Maryland Day event.This project aims to understand when and where, and how and how much, the energy conversion associated with non-equilibrium VDFs occurs during dayside magnetopause reconnection. Scientific questions: (1) When and where does energy conversion associated with non-equilibrium VDFs, as measured by the kinetic entropy, occur in different regions of 2.5-dimensional (2.5D) asymmetric magnetic reconnection, and what do they imply about the mechanisms of energy conversion? (2) What are the differences of energy conversion processes occurring for different conditions of guide field strengths and diamagnetic drift speeds in 2.5D asymmetric magnetic reconnection? (3) What are the differences of energy conversion processes occurring between 2.5D and 3D asymmetric reconnection? Methodology: Using particle-in-cell simulations, the team will analyze (1) the presence of wave activity, (2) whether VDFs evolve towards or away from Maxwellianity, and (3) the presence of chaotic motions. By comparing these results, they will find where higher order moments are participating in energy conversion and disentangle whether the waves are energizing particles or non-Maxwellian VDFs are generating waves. Using the time evolution of non-Maxwellianity to understand wave-particle interactions is a brand-new technique. The results will be compared to Magnetospheric Multiscale (MMS) observations. This project is directly relevant to the GEM Focus Group, “Magnetic Reconnection in the Age of the Heliophysics System Observatory”.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.

白天磁层顶重联控制着太阳风向磁层的等离子体和能量输入。它与显着的等离子体加热和粒子加速有关，但这些过程尚不清楚。原因之一是功、内能和热之间的能量转换传统上是根据麦克斯韦分布定义的，并用速度分布函数 (VDF) 的低阶矩来测量，但在无碰撞等离子体中，VDF 经常出现在非麦克斯韦状态。这种非平衡分布可能不稳定，会产生不稳定性和等离子体波，从而通过自洽的波粒相互作用影响 VDF。该项目研究与非平衡 VDF 相关的能量转换，这是理解和预测空间天气的重要研究。这项工作支持了一名早期职业 PI 和一名来自 STEM 领域代表性不足的群体的博士后。本科生将通过一年一度的马里兰日活动接受指导和推广。该项目旨在了解白天磁层顶重新连接期间与非平衡 VDF 相关的能量转换何时、何地、如何以及多少发生。科学问题：（1）通过动熵测量，与非平衡VDF相关的能量转换何时何地发生在2.5维（2.5D）不对称磁重联的不同区域中，它们对能量转换机制意味着什么？ (2) 2.5维非对称磁重联中不同导流场强和反磁漂移速度条件下能量转换过程有何差异？ (3) 2.5维和3维非对称重联的能量转换过程有何不同？方法：使用细胞内粒子模拟，团队将分析 (1) 波活动的存在，(2) VDF 是否朝着或远离麦克斯韦态演化，以及 (3) 混沌运动的存在。通过比较这些结果，他们将发现高阶矩在哪里参与能量转换，并解开波是激发粒子还是非麦克斯韦 VDF 产生波。利用非麦克斯韦性质的时间演化来理解波粒相互作用是一种全新的技术。结果将与磁层多尺度（MMS）观测结果进行比较。该项目与 GEM 焦点小组“太阳物理系统天文台时代的磁重联”直接相关。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。