Collaborative Research: Large Scale Structures and Solar Wind Origin from Eclipse Observations of Coronal Lines

太阳风是太阳系的关键组成部分，塑造了行星际空间和行星大气。了解控制其膨胀的基本物理过程是了解太阳与太阳系耦合的关键。随着我们越来越依赖载人和无人飞行任务进入空间，这一知识的重要性变得更加重要。 具体来说，尽管对太阳风进行了数十年的观测和理论研究，但我们仍然远远没有就太阳风在哪里以及如何加速达成共识。 太阳风的研究通常采用两种完全不同的技术：对日光层中局部风等离子体特性的现场测量，以及对距离太阳表面约1.5个太阳半径的区域进行遥感（光谱学和成像）。然而，在1.5到4个太阳半径之间的日冕区域，太阳风继续加速，大部分尚未探索。 日全食事件提供了罕见的，独特的机会，以获得观测这一关键地区的日冕。这项研究合作背后的基本思想是利用最近和即将到来的日全食事件期间对日冕的观测，以获得该地区太阳风参数的测量结果，其中许多将是第一次。日全食是一种独特的天文现象，能激发人们的想象力。 该团队在公共宣传和普通教育方面取得了成功，这些努力建立在这种简单的魅力之上，以提高公众对科学研究的认识，并吸引年轻人对科学的兴趣。将雇用和培训夏威夷大学天文学研究所的一名研究生参加这项研究，这项工作将构成该研究生论文的重要部分。 本科生的参与将通过现有的本科生研究机会计划被纳入密歇根大学的研究中，该项目不收取任何费用。该研究项目的目的是调查1.5至4个太阳半径之间的日冕区域，在那里太阳风继续加速，其电荷态成分冻结。在这一区域，重离子的演化成为太阳风加热和加速过程的直接探测器。本研究利用日食观测铁离子连续电离阶段发射的可见谱线来研究大尺度日冕。将使用线对连续体和线对线强度比来构建铁冻结位置的地图。将测量冻结的电荷状态，并将其与现场测量结果进行直接比较，从而将遥感和现场观测联系起来。诊断将把现有的CHIANTI光谱代码与用户定义的太阳风速度、温度和密度结合起来。预测的谱线强度将与日食观测结果进行比较，输入的等离子体参数将被修改，直到达成一致。由此产生的太阳风等离子体参数的经验模型将能够区分不同的候选风源区域，并将提供太阳风加热和加速模型的约束。

The solar wind is the key component of the solar system that shapes the interplanetary space and planetary atmospheres. Understanding the underlying physical processes controlling its expansion is key to understanding the coupling of the Sun to the solar system. The importance of this knowledge is becoming all the more critical with our increased reliance on access to space by manned and unmanned missions. Specifically, despite decades of observational and theoretical studies devoted to the solar wind, we are still far from a consensus on where and how the solar wind is accelerated. The solar wind is usually studied with two completely different techniques: in-situ measurements of local wind plasma properties in the heliosphere, and remote sensing (spectroscopy and imaging) of regions closer than roughly 1.5 solar radii to the solar surface. The region of the solar corona between 1.5 and 4 solar radii, where the solar wind continues to accelerate, however, is largely unexplored. Total solar eclipse events offer rare, unique opportunities to obtain observations of this crucial region of the solar corona. The basic idea behind this research collaboration is to utilize observations of the solar corona during recent and upcoming total solar eclipse events to obtain measurements of solar wind parameters for this region, many of which will be first of its kind. Total solar eclipses are unique astronomical events that capture people's imagination. The team has a successful record of public outreach and general education efforts that build on this easy fascination to raise public awareness of scientific research and engage young people's interest in science. A graduate student at the University of Hawaii Institute for Astronomy will be hired and trained to participate in this research and this work will constitute a significant part of that person's dissertation. Undergraduate student participation will be integrated into the research at the University of Michigan through the existing Undergraduate Research Opportunities Program there at no cost to this project. This research project is aimed at investigating the coronal region between 1.5 and 4 solar radii, where the solar wind continues to accelerate and its charge state composition freezes-in. In this region the evolution of heavy ions becomes a direct probe of solar wind heating and acceleration processes. This research uses eclipse observations of visible lines emitted by consecutive stages of ionization of iron to study the large-scale corona. Line-to-continuum and line-to-line intensity ratios will be used to build a map of the iron freeze-in location. Frozen in charge states will be measured and directly compared to in-situ measurements, linking remote sensing and in-situ observations. Diagnostics will couple the existing CHIANTI spectral code with user-defined velocity, temperature, and density of the solar wind. Predicted line intensities will be compared to eclipse observations, and the input plasma parameters will be modified until agreement is reached. The resulting empirical model of solar wind plasma parameters will be able to discriminate between different candidate wind source regions and will provide a constraint for solar wind heating and acceleration models.