Collaborative Research: SHINE--Exploring Reconnection-Driven Solar Explosive Events in Different Regimes through Modeling and Observation

磁重联是驱动太阳爆炸的机制，从纳米耀斑、紫外线爆发到行星际大小的日冕物质抛射。在重联的核心是一个电流片，其中磁能被转换为等离子体动能。这个项目研究等离子体不稳定如何导致重联和太阳爆炸。磁重联是空间天气的主要驱动因素，也是空间物理学、核聚变科学和天体物理学的重要基础物理过程。这项工作支持职业生涯中期和早期科学家的研究，包括研究生支持。该团队将通过美国宇航局的太阳物理学暑期学校为代表性不足的群体的本科生开设讲座。最近的理论分析和数值模拟表明，重联电流片可以自发地变得不稳定到等离子体不稳定。等离子体不稳定性将重新连接的电流片断裂成次级电流片、等离子体和通量绳，促进了快速重新连接的开始。等离子体介导的重连接可以导致多种动力学行为，这取决于与动力学尺度相关的碰撞和整体系统大小。适当地捕捉动力学行为的关键性质对于模拟爆炸事件至关重要。该项目将通过跨学科的数值模拟和太阳观测，深入了解等离子体介导的快速重联在不同体制下的发生和饱和。这是通过以下方式实现的：(1)对太阳爆炸事件进行数值模拟，包括日冕中的大规模日冕物质抛射和太阳低层大气中的紫外线爆炸事件。这些事件涵盖了广泛的长度尺度、等离子体密度和温度，对应于不同参数制度下的重联。模拟结果将与观测结果进行比较。(2)研究了不同参数下快速重联的开始和饱和。为了建立对各种模型在不同状态下的行为的基本理解，该团队将使用电阻磁流体动力学（MHD）、霍尔磁流体动力学（Hall MHD）和多矩多流体代码在控制良好的电流片中进行二维和三维重联模拟，以测试微观物理描述如何影响大规模、可观察尺度上快速重联的开始和饱和。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。

Magnetic reconnection is the mechanism driving explosions on the Sun ranging from nanoflares, ultraviolet bursts, to inter-planetary sized coronal mass ejections. At the core of reconnection is a current sheet where magnetic energy is converted to plasma kinetic energy. This project investigates how plasmoid instabilities lead to reconnection and solar explosions. Magnetic reconnection is a primary driver of space weather and an important fundamental physical process important to space physics, fusion science, and astrophysics. The work supports research of mid-career and early career scientists, including graduate student support. The team will develop lectures to undergraduate students from under-represented groups through NASA’s Heliophysics Summer School.Recent theoretical analyses and numerical simulations predict that reconnection current sheets can spontaneously become unstable to the plasmoid instability. The plasmoid instability fractures the reconnecting current sheet into secondary current sheets, plasmoids, and flux ropes, facilitating the onset of fast reconnection. Depending on the collisionality and global system size in relation to kinetic scales, plasmoid-mediated re- connection can result in a variety of dynamical behaviors. Appropriately capturing critical properties of the dynamical behaviors is crucial for modeling explosive events. This project will develop a deeper understanding of the onset and saturation of plasmoid-mediated fast reconnection in various regimes through a concerted interdisciplinary effort of numerical simulation and solar observation. This is accomplished by: (1) Performing numerical simulations of solar explosive events including large-scale coronal mass ejections in the solar corona and ultraviolet burst events in the lower solar atmosphere. These events cover a broad range of length scales, plasma densities, and temperatures, corresponding to reconnection in different parameter regimes. Simulation results will be compared with observations. (2) Investigating the onset and saturation of fast reconnection in different parameter regimes. To establish a basic understanding of how various models behave in different regimes, the team will conduct 2D and 3D simulations of reconnection in a well-controlled current sheet using resistive magnetohydrodyamic (MHD), Hall MHD, and multi-moment multi-fluid codes to test how microscopic physics descriptions affect the onset and saturation of fast reconnection at large, observable scales.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.