Understanding Wave Energy Transport Through the Complex Chromosphere and Transition Region

等离子体波似乎对太阳色球、过渡区和日冕的大部分加热负责。光球层中的流体运动为波提供了能量，但精确的激发机制尚不清楚。一旦被激发，波能必须被传递到日冕。然而，最近的观测表明，光球和日冕之间的界面区域(即色球和过渡区)是复杂的。这样，就知道了波能是如何通过界面区域传播的。这些问题阻碍了日冕加热模型的发展，限制了我们对日冕底部波动特性的了解。为了解决太阳物理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中的波的特性。该项目的主要科学目标是：(1)确定等离子体波在哪里产生；(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，将分析IRIS的档案数据，以解决以下三个主要问题。首先，确定MHD波在哪里产生。目前尚不清楚波是主要在光球中产生并通过界面区向上传播，还是在界面区内产生。光球体表现出各种可以产生波的流体运动，例如颗粒运动对磁力线的抖动。但是，波可以在过渡区被强烈的密度梯度反射，因此不能到达日冕。光球层的全球声波p模可以发射声波，但如果它们是日冕中观测到的Alfvenic波的来源，它们必须进行模式转换。或者，例如通过重新连接，可以在色球中产生波。IRIS数据将被用来通过界面区域的不同高度来确定波浪模式以及波浪功率的源和汇，从而确定这些过程和其他可能过程的特征。第二，测量从光球层到日冕的波的传播。波的反射和衰减可能会阻止大部分的波能到达日冕。该项目将通过观察波沿建筑物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。然后将这些测量结果与较低位置的光球波动和较高位置的日冕中的Alfvenic波的现有观测和光谱进行比较。分析将确定Alfvenic波在哪里被反射，是否存在波功率从纵模到横模的转换，或者反之亦然，以及波能在哪里耗散。结果将与波在这一复杂区域的传播、反射和衰减的理论进行比较。第三，也是最后，表征日冕底部的波模式和功率，以便提供日冕加热模型所需的临界边界条件。通过比较速度和强度起伏的幅度和相位，可以限制可压缩波和不可压缩波的相对贡献。虹膜有足够的空间分辨率来观察扭转振荡，从而估计扭转波与扭结波的Alfvenic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中发展到更高的高度。这项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。该项目将在太阳物理领域和光谱观测分析技术方面培训一名博士后研究科学家。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。

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.