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.

作为这个为期三年的项目的一部分，这项调查将大大增加我们对太阳内部地下流动物理学的了解，从而确定它们随磁区特性和时间的变化。 该研究计划旨在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组成部分。 子午流在导致太阳极地极性反转的过程中起着至关重要的作用，并能够预测后续太阳周期的特性。 目前尚不清楚它是如何通过活跃区域相关流入的贡献进行及时调节的。 本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。 人们已经提出了有关流动物理学的理论，并预测了它们随深度的变化。 作为该项目的一部分，这些预测将通过逆向建模工作进行测试。 利用数值 MHD 模拟提供的人工数据，研究活动还将旨在开发和验证可靠地推断地下流动的方法，并避免因表面磁场对地震波的影响而造成的伪影。 这些方法对于改进和验证通过日震学推断的其他流和结构模型将具有不可估量的价值。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进行全面的、高空间分辨率的日震调查，以改进太阳发电机模型。 该研究项目有四个主要目标。第一个目标是利用 SDO 任务上的日震成像仪对多普勒图应用日震全息术来表征太阳活动区域周围观测到的近地表流。 该表征将包括检查流动特性与磁通量的依赖性。 还将研究区域演变时流量的时间依赖性。 第二个目标是确定并量化活动区域周围近地表流对全球经向和纬向流模式的纬度和时间变化的贡献。 这将通过将活动区域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反演模型确定活动区域相关流的深度依赖性，以便提供对流的物理理解。 第四个目标是验证活动区域周围流量确定的可靠性。 这将使用从磁结构附近的波的最先进的数值 MHD 模拟中获得的现有合成数据来实现。为了改进太阳发电机的表面通量输运模型，需要了解太阳内部活动区域相关流对更大规模动力学的贡献。 该项目的成果预计将提高人们对太阳和恒星发电机以及磁场演化的常识。 预期结果将有助于改进对太阳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，以供这些类型的模型使用。 该项目将促进团队继续参与科罗拉多大学博尔德分校主办的 REU 太阳和空间物理项目。 这项研究的很大一部分是由一名博士后研究科学家进行的，他将领导多项项目任务。 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。