Understanding Wave Energy Transport Through the Complex Chromosphere and Transition Region

了解复杂色球层和过渡区域的波能传输

• 批准号: 1834822
• 负责人: Michael Hahn
• 金额: $ 41.84万
• 依托单位: Columbia University
• 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=1834822&HistoricalAwards=false
• 关键词: Understanding; Wave; Energy; Transport; Through

Plasma waves appear to be responsible for much of the heating of the chromosphere, transition region, and corona of the Sun. Fluid motions in the photosphere provide power for the waves, but the precise excitation mechanism is yet unknown. Once excited, the wave energy must be transmitted to the corona. However, recent observations have shown that the interface region between the photosphere and corona (i.e., the chromosphere and transition region) is complex. Thus, it is known how wave energy propagates through the interface region. These issues hinder the development of coronal heating models, which are limited by our poor understanding of the wave properties at the base of the corona. To tackle these important science problems for solar physics, this three-year project will use data from the Interface Region Imaging Spectrometer (IRIS) to measure the properties of waves in the interface region of the solar atmosphere. The main science objectives of the project are to: (1) identify where plasma waves are generated; (2) determine how wave energy propagates from the photosphere to the corona; and, (3) specify the wave boundary conditions at the base of the corona.During this three-year research project, archival data from IRIS will be analyzed to address the following three major issues. First, determine where MHD waves are generated. It is currently unknown whether waves are generated mainly in the photosphere and propagate up through the interface region or whether the waves are generated within the interface region. The photosphere exhibits various fluid motions that can generate waves, such as the buffeting of magnetic field lines by granular motions. But, the waves can be reflected by the strong density gradients at the transition region and so not reach the corona. Global acoustic p-modes at the photosphere could launch acoustic waves, but they must undergo mode conversion if they are the source of the Alfvenic waves observed in the corona. Alternatively, waves may be generated in the chromosphere, for example, by reconnection. The IRIS data will be used to determine the wave modes and sources and sinks of wave power through varying heights in the interface region and thereby identify signatures of these processes and other possible ones. Second, measure the propagation of waves from the photosphere into the corona. Wave reflection and damping may prevent much of the wave power from reaching the corona. This project will determine how waves are transmitted through the interface region by observing the propagation of waves along structures and by measuring the power spectrum of the waves. These measurements will then be compared to existing observations and spectra of lower lying photospheric fluctuations and of Alfvenic waves in the higher lying corona. The analysis will determine where Alfvenic waves are reflected, if there is conversion of wave power from longitudinal to transverse modes or vice versa, and where wave energy is dissipated. Results will be compared to theories for the propagation, reflection, and damping of waves throughout this complex region. Third and final, characterize the wave modes and power at the base of the corona in order provide the critical boundary conditions needed for models of coronal heating. By comparing the amplitudes and phases of velocity and intensity fluctuations one can constrain the relative contribution of compressible versus incompressible waves. IRIS has sufficient spatial resolution to see torsional oscillations and thereby estimate the Alfvenic wave energy content of torsional versus kink waves. By studying the power spectrum of the waves, it will be determined whether the fluctuations are already turbulent at the base of the corona or whether the turbulence develops in the corona at larger heights.This research project will have broader impacts through postdoctoral training and public outreach. The project will train a postdoctoral research scientist in the field of solar physics and in techniques for the analysis of spectroscopic observations. 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.

等离子体波似乎是太阳色球层、过渡区和日冕加热的主要原因。 光球层中的流体运动为波提供了动力，但精确的激发机制尚不清楚。 一旦被激发，波能必须被传输到日冕。 然而，最近的观测表明，光球和日冕之间的界面区域（即，色球层和过渡区）是复杂的。因此，已知波能如何通过界面区域传播。 这些问题阻碍了日冕加热模型的发展，这是有限的，我们对日冕底部的波动特性的了解不足。 为了解决太阳物理学的这些重要科学问题，这个为期三年的项目将使用界面区域成像光谱仪（IRIS）的数据来测量太阳大气界面区域的波特性。 该项目的主要科学目标是：（1）确定等离子体波产生的位置;（2）确定波能量如何从光球层传播到日冕;以及（3）确定日冕底部的波边界条件。在这个为期三年的研究项目中，IRIS的档案数据将被分析以解决以下三个主要问题。 首先，确定MHD波产生的位置。 目前尚不清楚波是否主要在光球层中产生并通过界面区域向上传播，或者波是否在界面区域内产生。 光球呈现出各种可以产生波的流体运动，例如颗粒运动引起的磁力线抖动。 但是，波可以被过渡区的强密度梯度反射，因此不能到达日冕。 光球层的全局声波p模可以发射声波，但如果它们是日冕中观测到的阿尔文波的源，它们必须经历模式转换。 另一种情况是，色球层中可能会产生波，例如，通过重连。 IRIS数据将用于确定波浪模式以及通过界面区域不同高度的波能源和汇，从而确定这些过程和其他可能过程的特征。 其次，测量波从光球层到日冕的传播。 波的反射和衰减可能会阻止大部分波能到达日冕。 该项目将通过观察波沿着结构的传播和测量波的功率谱来确定波如何通过界面区域传播。 这些测量结果，然后将比较现有的观测和光谱较低的光球波动和Alfvenic波在较高的谎言日冕。 分析将确定阿尔文波反射的位置，波能是否从纵向模式转换为横向模式或反之亦然，以及波能耗散的位置。 结果将进行比较的传播，反射和阻尼波在整个这个复杂的区域的理论。 第三，也是最后一个，描述日冕底部的波模式和功率，以便为日冕加热模型提供所需的临界边界条件。 通过比较速度和强度波动的振幅和相位，可以限制可压缩波与不可压缩波的相对贡献。 IRIS具有足够的空间分辨率，可以看到扭转振荡，从而估计扭转波与扭结波的阿尔文波能量含量。 通过研究波的功率谱，将确定波动在日冕底部是否已经是湍流，或者湍流是否在日冕的更高高度发展。该研究项目将通过博士后培训和公众宣传产生更广泛的影响。 该项目将培训一名太阳物理学和光谱观测分析技术方面的博士后研究科学家。 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。

项目成果

Evidence for Parametric Decay Instability in the Lower Solar Atmosphere

• DOI: 10.3847/1538-4357/ac7147
• 发表时间: 2022-04
• 期刊: The Astrophysical Journal
• 作者: Michael Hahn;Xiangrong Fu;D. Savin

Characteristics of Nanoflare Heating in a Coronal Bright Point

日冕亮点纳耀斑加热的特征

• DOI: 10.3847/1538-4357/ac897f
• 发表时间: 2022
• 期刊: The Astrophysical Journal
• 作者: Hahn, Michael;Ho, Brandon;Savin, Daniel Wolf
• 通讯作者: Savin, Daniel Wolf