A Helioseismic Study of Active Region Flows and their Contribution to Global Dynamics

活动区域流及其对全球动力学贡献的日震研究

• 批准号: 1623844
• 负责人: Douglas Braun
• 金额: $ 36.7万
• 依托单位: NorthWest Research Associates, Incorporated
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-01-15 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1623844&HistoricalAwards=false
• 关键词: Helioseismic; Study; Active; Region; Flows

The survey to be produced as part of this 3-year project will considerably increase our knowledge about the physics of subsurface flows inside the Sun, allowing their variation with magnetic region properties, and with time, to be ascertained. The research program seeks to understand how these flows affect larger circulation patterns, particularly the meridional and zonal flow components of global circulation. The meridional flow is involved critically in the process that leads to Sun's polar field polarity reversals and the ability to predict properties of subsequent solar cycles. It is not clear how it is modulated in time by the contribution of active-region related inflows. A quantitative assessment of this contribution, provided by this research project, will allow critical improvements to be made in predictive models. Theories regarding the physics of the flows have been put forward, with predictions about their variation with depth. These predictions will be tested by the inverse modeling efforts as part of this project. Using artificial data available from numerical MHD simulations, the research activities will also aim to develop and validate methods to infer subsurface flows reliably and which avoid artifacts caused by the influence of surface magnetic fields on the seismic waves. These methods will be invaluable for improving and validating other models of flows and structures inferred through helioseismology.The main purpose of this 3-year project is to perform a comprehensive, high-spatial-resolution helioseismic survey of subsurface flows around solar magnetic regions in order to improve models of solar dynamo. The research project has four main objectives. The first objective is to characterize, using helioseismic holography applied to Dopplergrams from the Helioseismic Imager onboard the SDO mission, the near-surface flows observed around solar active regions. This characterization will include examining the dependence of the flow properties with magnetic flux. The time dependence of the flows as regions evolve will also be examined. The second objective is to establish and quantify the contribution of the near-surface flows surrounding active regions to the latitudinal- and temporal-variation of the global meridional and zonal flow patterns. This will be achieved by comparing monthly time and longitude averages of active-region related flows with meridional and zonal flow measurements. The third objective is to determine, through helioseismic inverse modeling, the depth dependence of active-region related flows, in order to provide a physical understanding of the flows. The fourth objective is to validate the reliability of the flow determination around active regions. This will be achieved using existing synthetic data derived from state-of-the-art numerical MHD simulations of waves in the vicinity of magnetic structures.An understanding of the contribution of active-region-related flows in Sun's interior to the larger-scale dynamics is required for improving surface-flux-transport models of the solar dynamo. The outcome of this project is expected to improve general knowledge of solar and stellar dynamos and the evolution of magnetic fields. The expected results will allow improvements in predicting the solar-cycles of the Sun. The project team will broadly disseminate data products for their use in these types of models as part of this program. This project will facilitate continued involvement of the team in the REU Program in Solar and Space Physics hosted by the University of Colorado at Boulder. A considerable portion of this research is being carried out by a postdoctoral research scientist who will take the lead on several of the project tasks. The research and EPO agenda of this project supports the Strategic Goals of the AGS Division in discovery, learning, diversity, and interdisciplinary research.

作为这项为期3年的项目的一部分，这项调查将极大地增加我们对太阳内部地下流动的物理知识，从而使我们能够确定它们随磁区性质和时间的变化。该研究计划试图了解这些流动如何影响更大的环流模式，特别是全球环流的经向和纬向流动成分。在导致太阳极场极性反转和预测后续太阳活动周期的能力的过程中，经向流起了至关重要的作用。目前尚不清楚与活跃地区相关的资金流入的贡献如何及时对其进行调制。这一研究项目提供的对这一贡献的定量评估将使预测模型得到重大改进。已经提出了关于水流物理的理论，并对其随深度的变化进行了预测。作为该项目的一部分，这些预测将通过反向建模工作进行验证。利用数值MHD模拟提供的人工数据，研究活动还将致力于开发和验证可靠地推断地下流动的方法，并避免地表磁场对地震波的影响造成的伪影。这些方法对于改进和验证其他通过日震学推断的流动和结构模型将是非常有价值的。这个为期3年的项目的主要目的是对太阳磁区周围的地下流动进行全面的、高空间分辨率的日震调查，以改进太阳发电机的模型。该研究项目有四个主要目标。第一个目标是利用应用于SDO任务上日震成像仪的多普勒图的日震全息术，描述观测到的太阳活动区周围的近地表流动。这种表征将包括考察流动特性与磁通量的依赖关系。随着区域的发展，流动的时间依赖性也将被考察。第二个目标是确定和量化活动区周围的近地表流动对全球经向和纬向流动模式的纬度和时间变化的贡献。这将通过将活跃区相关流量的月时间和经度平均值与经向和纬向流量测量值进行比较来实现。第三个目标是通过日震逆模拟确定与活动区有关的流动的深度相关性，以便提供对流动的物理了解。第四个目标是验证活动区域周围流动确定的可靠性。这将利用现有的合成数据来实现，这些数据来自对磁结构附近波的最先进的MHD数值模拟。为了改进太阳发电机的表面通量传输模型，需要了解太阳内部与活动区相关的流动对更大尺度动力学的贡献。该项目的成果预计将增进关于太阳和恒星发电机以及磁场演变的一般知识。预期的结果将有助于改进对太阳活动周期的预测。作为该计划的一部分，项目团队将广泛传播数据产品，以便在这些类型的模型中使用。该项目将促进该小组继续参与由科罗拉多大学博尔德分校主办的太阳和空间物理REU计划。这项研究的相当大一部分是由一位博士后研究科学家进行的，他将领导几项项目任务。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。