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

使用数据驱动的磁流体动力 (MHD) 方法对太阳喷发三维 (3D) 标准模型进行批判性评估

基本信息

批准号：
1841962
负责人：
KD Leka
金额：
$ 34.15万
依托单位：
NorthWest Research Associates, Incorporated
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2019
资助国家：
美国
起止时间：
2019-05-15 至 2023-04-30
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1841962&HistoricalAwards=false
关键词：
Critical Assessment Three dimensional 3D

项目摘要

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.

太阳爆发的理论模型是由使用简单磁场和速度场的数值MHD计算支持的。然而，太阳要复杂得多，因此尚不清楚在理想条件下工作的模型是否与实际的太阳相似。这个为期三年的研究项目的目的是测试一种流行的太阳爆发模型，即“标准3D模型”，在现实条件下，通过利用光球观测来模拟真实的太阳爆发，从而驱动活跃的区域尺度日冕MHD模拟。项目团队将投入大量的时间和精力，将他们的数值模拟与实际的太阳观测结果进行比较。研究将分为三个部分：(i)执行数据驱动的MHD模拟；（ii）将模拟与观测进行比较；（iii）使用模拟来测试“标准3D模型”的预测。对于喷发区域的样本，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。这些外推将用于初始化零β MHD模拟，这些模拟是由使用一致处理感应方程的光流方法从光谱偏振数据推断出的流图驱动的。该团队还将建立一组非喷发区域的模型，作为一个重要的控制：他们的目标是证明，当现实中没有火山喷发时，他们的方法不会产生火山喷发。他们将使用他们的模拟来测试“标准3D模型”的预测，该模型涉及导致喷发的不稳定机制（例如，环面不稳定）和喷发期间的重连接模式（例如，滑动重连接）。控制区域的包含将表明这些特征是否对喷发的发生至关重要，而不仅仅是简单地存在，但在喷发过程中仍然不重要。该团队将在他们的模拟中确定不稳定机制，重新连接的位置和性质。迄今为止，太阳爆发的“标准3D模型”已经通过MHD模拟和简单的双极磁场进行了广泛的测试。这个为期三年的研究项目迈出了重要的下一步，即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，这在一般的天体物理学背景下是重要的。该研究项目的一个新颖方面是大量的工作致力于验证数据驱动的MHD模拟；尽管近年来这种类型的模拟变得越来越普遍，但它们的验证通常是次要考虑因素，并且通常依赖于模拟中EUV回路和场线之间的肉眼比较。项目团队将投入大量的时间和精力来开发用于在模拟和观察之间进行定量比较的度量，这是客观验证的必要步骤。这个为期三年的项目的预期结果将引起空间气象界的兴趣：提高对太阳爆发的了解也将提高我们对这些事件的预测能力。作为该项目的一部分，将开发用于比较数值模拟与实际观测的方法和指标，这些方法和指标将普遍用于太阳能社区；项目团队将把他们的工具提供给更广泛的在线社区。他们所有的项目数据也将向公众开放。该团队还计划在项目的最后一年在SHINE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。