Critical Assessment of the Three-dimensional (3D) Standard Model of Solar Eruptions Using a Data-driven MagnetoHydroDynamic (MHD) Approach

太阳喷发的理论模型得到了使用简单磁场和速度场的数值MHD计算的支持。然而，太阳要复杂得多，因此还不清楚在理想条件下工作的模型是否类似于实际的太阳。这个为期三年的研究项目的目的是在现实条件下测试一种流行的太阳喷发模型-标准3D模型，方法是使用光球层观测来模拟真实的喷发，以驱动活动区范围的日冕MHD模拟。该项目团队将花费大量的时间和精力来将他们的数值模拟与真实的太阳观测结果进行比较。这项研究将包括三个部分：(I)执行数据驱动的MHD模拟；(Ii)将模拟与观测进行比较；以及(Iii)使用模拟来测试“标准3D模型”的预测。对于喷发区的样本，该项目团队将在每次喷发前大约一小时，从矢量磁图中构建非线性无力外推。这些外推将被用来初始化零贝塔MHD模拟，该模拟由从光谱偏振数据推断的流图驱动，使用一致地处理感应方程的光流方法。该团队还将模拟一组非喷发区域作为重要的控制措施：他们的目标是证明他们的方法在实际没有喷发的情况下不会产生喷发。他们将使用他们的模拟来测试“标准3D模型”关于导致喷发的不稳定机制(例如，环面不稳定)和喷发期间的重新连接模式(例如，滑动重新连接)的预测。控制区的包含将表明这些特征是否对喷发的发生至关重要，而不仅仅是存在于喷发过程中，而是保持不重要。该团队将在他们的模拟中确定重联的不稳定机制、地点和性质。到目前为止，太阳喷发的“标准3D模型”已经使用简单的双极磁场的MHD模拟进行了广泛的测试。这个为期三年的研究项目迈出了重要的下一步，在现实条件下测试该模型。这项工作的智力价值在于建立了“标准3D模型”的可行性。该项目还旨在为太阳大气中磁能储存和释放的基本机制提供新的物理见解，这在一般天体物理背景下是重要的。该研究项目的一个新方面是致力于验证数据驱动的MHD模拟的大量工作；尽管这种类型的模拟在最近几年变得越来越常见，但它们的验证通常是次要的考虑因素，例如，它经常依赖于EUV环路和来自模拟的场线之间的目测比较。项目组将投入大量时间和精力来制定在模拟和观测之间进行定量比较的指标，这是客观验证的必要步骤。这一为期三年的项目的预期结果将引起空间气象界的兴趣：对太阳喷发的更好理解也将提高我们对这些事件的预测能力。将作为该项目的一部分开发的将数值模拟与实际观测进行比较的方法和指标将普遍适用于太阳能社区；项目组将在网上向更广泛的社区提供他们的工具。他们的所有项目数据也将向公众开放。该小组还计划在该项目的最后一年在SISH研讨会上组织一次特别会议，重点是使用不同的MHD模型对3D标准模型进行批判性评估。该项目的研究和EPO议程支持AGS部门在发现、学习、多样性和跨学科研究方面的战略目标。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Theoretical models of solar eruptions are supported by numerical MHD calculations that use simple magnetic and velocity fields. The Sun, however, is much more complex, and it is therefore unclear whether models that work under ideal conditions resemble on the actual Sun. The aim of this three-year research project is to test a popular model of solar eruptions, "the standard 3D model," under realistic conditions by modeling real eruptions using photospheric observations to drive active-region-scale coronal MHD simulations. The project team will devote a significant amount of time and effort to compare their numerical simulations to real solar observations. The research study will have three parts: (i) perform data-driven MHD simulations; (ii) compare the simulations with observations; and, (iii) use the simulations to test predictions of "the standard 3D model." For a sample of eruptive regions, the project team will construct nonlinear force-free extrapolations from vector magnetograms, about an hour before each eruption. These extrapolations will be used to initialize the zero-beta MHD simulations driven by flow maps inferred from spectro-polarimetric data using optical-flow methods that treat the induction equation consistently. The team will also model a set of non-eruptive regions as an important control: they will aim to demonstrate that their method does not produce eruptions when none occurs in reality. They will use their simulations to test the predictions of "the standard 3D model" regarding the instability mechanism responsible for eruption (e.g., torus instability) and mode of reconnection during the eruption (e.g., slipping reconnection). The inclusion of control regions will indicate whether or not these features are essential for an eruption to occur, and not just simply being present but remain unimportant during the eruption process. The team will identify the instability mechanism, sites and nature of reconnection in their simulations.To date, "the standard 3D model" of solar eruptions has been tested extensively using MHD simulations with simple bipolar magnetic fields. This three-year research project takes the important next step to test the model under realistic conditions. The intellectual merit of this work is to establish the viability of "the standard 3D model." The project also aims to provide new physical insight into the basic mechanisms of magnetic energy storage and release in the solar atmosphere, which are important in a general astrophysical context. A novel aspect of the research project is the significant amount of work devoted to validating the data-driven MHD simulations; although this type of simulations is becoming increasing common in recent years, their validation is typically of a secondary consideration and it often relies on by-eye comparisons between EUV loops and field lines from the simulation, for example. The project team will devote a significant amount of time and effort to developing metrics for making quantitative comparisons between simulations and observations, which is a necessary step for objective validation.The anticipated results of this three-year project will be of interest to the space weather community: an improved understanding of solar eruptions will also improve our predictive capability for these events. The methodology and metrics for comparing numerical simulations to real observations that will be developed as part of this project will be of general use to the solar community; the project team will make their tools available to the broader community online. All their project data will be made available to the public too. The team also plans to organize a special session at the SHINE Workshop in the last year of the project focused on critically assessing the 3D standard model using different MHD models. The research and EPO agenda of this project supports the Strategic Goals of the AGS Division in discovery, learning, diversity, and interdisciplinary research.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.