Embedding Force-Free Flux Ropes in Potential Magnetic Fields

日冕物质抛射(CME)和耀斑等太阳喷发现象造成了一些最严重的空间天气影响。它们被认为是由于日冕中磁能的爆炸性释放造成的，而日冕中的磁场目前无法直接测量。这一研究项目有望导致对空间天气的物理驱动因素进行更好的建模和更深入的理解。对日冕物质抛射的根本原因(S)以物理学为基础的理解最终可导致对空间气象事件的更好预报，从而有可能采取缓解措施来保护人力和技术资产。要模拟太阳喷发现象，关键是要有一种有效的方法来从光球层的磁场数据中数值地构造喷发前的配置。在这个项目过程中将要开发的新方法预计将与现有的方法相比具有很强的竞争力，例如非线性无力场重建或磁绳插入，特别是在所产生的磁绳参数的效率和控制方面。这项调查是及时、可行的，并与NSF的日地研究计划直接相关，该计划“支持对各种形式的能量由太阳产生、传输到地球并最终储存在陆地环境中的过程的研究。”因此，该项目支持AGS司在发现、学习、多样性和跨学科研究方面的战略目标。到目前为止，许多此类模型都采用解析或半解析的磁绳模型作为喷发的基础。这个为期3年的项目旨在构建嵌入在环境势场中的柔性形状的无力磁绳的解析近似解，其中光球通量分布与观测场相匹配。对于实际CME事件的MHD模拟(进一步驱动)，将进一步放宽近平衡解析解，以达到近似数值稳定平衡作为初始状态。该项目将改进目前的铁托夫-德莫林(TD)无力磁绳模型，PI已开发的该模型允许磁绳的复杂形状/路径的灵活性，并保留观测到的磁图中的磁通分布。基于这种技术的喷发前构型的计算将是简单、高效的，所得到的模型将比迄今用于CME模拟的模型更准确。作为这项调查的一部分，项目组将提供产生平衡通量绳的公式和数字代码，以便太阳-日球界的其他研究人员能够在他们自己的代码中使用这些模型进行实验。

Solar eruptive phenomena, such as Coronal Mass Ejections (CMEs) and flares, cause some of the most severe space-weather effects. They are believed to result from an explosive release of magnetic energy in the solar corona, where the magnetic field cannot at present be measured directly. This research project is expected to lead to a better modeling and deeper understanding of the physical drivers of space weather. A physics-based understanding of the underlying cause(s) of CMEs can eventually lead to a better forecasting of space-weather events, which may allow mitigating steps to be taken to protect human and technological assets. To model solar eruptive phenomena, it is critical to have an efficient method for numerically constructing pre-eruptive configurations from photospheric magnetic data. The new method to be developed over the course of this project is expected to be highly competitive compared to the existing ones, such as the nonlinear force-free field reconstruction, or flux-rope insertion, especially in terms of the efficiency and control of the resulting flux-rope parameters. This investigation is timely, feasible, and directly related to the NSF's Solar Terrestrial Research Program that "supports research on the processes by which energy in diverse forms is generated by the Sun, transported to the Earth, and ultimately deposited in the terrestrial environment." Therefore, the project supports the Strategic Goals of the AGS Division in discovery, learning, diversity, and interdisciplinary research. To date, analytical or semi-analytical flux-rope models are being used as the basis for the eruption in many of these models. This 3-year project aims to construct analytically approximate solutions of a force-free flux rope of flexible shape embedded in an ambient potential field, with photosphere flux distribution matching the observed fields. The near-equilibrium analytic solution will be relaxed further with line-tied MHD simulations to reach an approximate numerical stable equilibrium as the initial state for MHD simulations (with further driving) of realistic CME events. The project will improve upon the current Titov-Demoulin (TD) force-free flux rope model the PI has developed to allow for the flexibility of complex shapes/paths of the flux rope and preserve the flux distribution in the observed magnetograms. The computation of pre-eruptive configurations based on this technique will be simple, highly efficient, and the resulting model will be significantly more accurate than those used in CME simulations so far. As part of this investigation, the project team will provide formulas and a numerical code for producing equilibrium flux ropes, so that other researchers from the solar-heliospheric community will be able to experiment using these models in their own codes.