Embedding Force-Free Flux Ropes in Potential Magnetic Fields

太阳爆发现象，如日冕物质抛射（CME）和耀斑，导致一些最严重的空间天气影响。 它们被认为是由于太阳日冕中的磁能爆炸性释放造成的，目前无法直接测量磁场。 这一研究项目预计将导致更好地建模和更深入地了解空间天气的物理驱动因素。 对日冕物质抛射根本原因的基于物理学的理解最终可以更好地预测空间天气事件，从而可以采取缓解措施来保护人力和技术资产。 为了模拟太阳爆发现象，关键是要有一个有效的方法，从光球磁数据的数值构造喷发前的配置。 与现有方法（如非线性无力场重建或磁绳插入）相比，在本项目过程中开发的新方法预计将具有很强的竞争力，特别是在效率和控制所产生的磁绳参数方面。 这项调查是及时的，可行的，并直接关系到美国国家科学基金会的日地研究计划，该计划“支持对太阳产生各种形式的能量，传输到地球，并最终沉积在陆地环境中的过程的研究。“因此，该项目支持AGS部门在发现，学习，多样性和跨学科研究方面的战略目标。 到目前为止，分析或半分析通量绳模型被用作许多这些模型的喷发的基础。 这个为期3年的项目的目的是构建分析近似解的力自由磁通绳的柔性形状嵌入在周围的潜在领域，光球通量分布匹配的观测领域。 近平衡的解析解将进一步放宽线绑MHD模拟，以达到近似的数值稳定平衡作为MHD模拟（进一步驱动）现实CME事件的初始状态。 该项目将改进PI开发的当前Titov-Demoulin（TD）无力通量绳模型，以允许通量绳的复杂形状/路径的灵活性，并保留观测到的磁图中的通量分布。 基于这种技术的喷发前配置的计算将是简单的，高效的，所产生的模型将显着更准确地比那些使用的CME模拟到目前为止。 作为这项调查的一部分，项目小组将提供用于产生平衡通量绳的公式和数字代码，以便太阳-日光层界的其他研究人员能够在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.