CAREER: Toward Understanding Solar Wind Turbulence in the Inner Heliosphere

确定加热日冕和加速太阳风的确切机制是太阳-日球层物理学中最重要的两个问题，也是帕克太阳探测器(PSP)任务的首要目标之一。这项计划于2018年夏天发射的任务将访问任何航天器从未探索过的近太阳区域，对9.5至55太阳半径(从太阳中心测量)之间的内日光层提供开创性的就地和近距离遥感测量，覆盖范围比太阳神任务近6倍。这项为期五年的职业计划旨在提高目前对太阳附近湍流的演变和结构的理解。该项目还将有助于阐明能量是如何从太阳表面传输到其上层大气的，以及这种能量是如何消散的，以加热太阳日冕并加速太阳风。该项目的主要广泛影响之一是，它将为解释PSP测量奠定理论基础，从而加强PSP飞行任务的科学回报，这将对日球层物理学中的其他一些悬而未决的问题产生影响。项目组将引入一种新颖和用户友好的软件工具，该工具将允许学生在最少的科学计算知识的情况下使用数值模拟，以加强对空间等离子体物理学入门的学习。数值模拟将在入门课程中发挥的作用将密切反映模拟在现代等离子体研究中所起的作用，即当分析进展不再可能时，促进对基本物理的理解。该软件界面将允许学生快速解决数值问题，从数值解中获得直觉，以帮助加强对基本概念的理解。该项目的另一个更广泛的主要影响是，最终将根据GNU开放源码许可证在网上提供该工具的经过充分测试和工作的版本，以便扩大其等离子体物理问题库并在其他研究机构中使用。这一软件工具还将用于向公众传播这一项目的研究成果，并向他们通报空间等离子体研究的相关性以及PSP将在未来几十年带来的革命性发现。这个职业项目的研究和EPO议程支持AGS司在发现、学习、多样性和跨学科研究方面的战略目标。这一职业有望提供对近太阳环境中湍流的起源和演变的更好理解，从低日冕中观察到的阿尔芬波到上层日冕和太阳风中的湍流波动。这项研究将结合理论、高分辨率数值模拟和现有观测，为解释PSP史无前例的测量结果奠定基础。该项目的目的是完成以下具体科学目标：(1)调查湍流如何从日冕中的AW运动演变到较大日心距离处的充分发展的AW湍流；(2)确定控制惯性范围功率谱的标度定律、交叉螺旋度和湍流中剩余能量的作用以及这些特性如何取决于日心距；(3)研究这种湍流在太阳活动中心的测量结果中所起的作用；(3)研究太阳冕观测到的波动磁能谱的指数规律；以及(4)建立PSP将测量的湍流波动特性的预测。这项职业调查也是及时的，因为它将在2018年年底提供第一批测量数据之前，为解释PSP信号奠定必要的理论和数字框架。这项研究的结果与未来的PSP观测结果相结合，不仅有助于扩大我们对该地区阿尔文湍流基本原理的了解，而且将导致在确定阿尔文湍流作为日冕加热和太阳风加速的主要机制的可行性方面取得变革性的进展。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。

Determining the exact mechanisms that heat the corona and accelerate the solar wind are two of the most important problems in solar-heliospheric physics, as well as one of the top priority goals of the Parker Solar Probe (PSP) mission. This mission, which is scheduled to launch in the summer of 2018, will visit the near-Sun regions never explored before by any spacecraft, providing groundbreaking in-situ and close-by remote sensing measurements of the inner heliosphere between 9.5 and 55 solar radii (measured from the center of the Sun), reaching up to six times closer than the Helios mission. This five-year CAREER project is aimed at improving present understanding of the evolution and structure of turbulence close to the Sun. The project will also help elucidate how energy is transported from the solar surface to its upper atmosphere and how this energy is dissipated to heat the solar corona and accelerate the solar wind. One of the main broader impacts of this project is that it will enhance the scientific return of the PSP mission by laying the theoretical foundations for interpretation of PSP measurements, which will have repercussions in a number of other outstanding questions in heliospheric physics. The project team will introduce a novel and user friendly software tool that will allow students to use numerical simulations, with minimal knowledge of scientific computing, to enhance learning of introductory space plasma physics. The role that numerical simulations will play in the introductory courses will closely mirror the role that simulations play in modern plasma research, i.e., to facilitate understanding of the underlying physics when analytical progress is no longer possible. The software interface will allow students to quickly solve numerical problems to gain intuition from the numerical solution to help reinforce understanding of the underlying concepts. Another main broader impact of this project is that, at its conclusion, a fully tested and working version of this tool will be made available online under the GNU open-source license, to allow for the expansion of its plasma physics problems base and use in other research institutions. This software tool will also be adapted to disseminate with the general public the research outcomes of this project, and inform them on the relevance of space plasma research and the revolutionary discoveries that the PSP will enable in the decades to come. The research and EPO agenda of this CAREER project supports the Strategic Goals of the AGS Division in discovery, learning, diversity, and interdisciplinary research.This CAREER is expected to provide an improved understanding of the origin and evolution of turbulence in the near-Sun environment, from the Alfven waves observed in the low corona to turbulent fluctuations in the upper corona and the solar wind. This investigation will combine theory, high-resolution numerical simulations and existing observations to lay the groundwork for the interpretation of the unprecedented measurements by the PSP. The project aims to accomplish the following specific science goals: (i) Investigate how turbulence evolves from AW motions in the solar corona to fully developed AW turbulence at larger heliocentric distances; (ii) identify scaling laws governing the inertial-range power spectrum, the role of cross- helicity and residual energy in the turbulence and how such properties depend on the heliocentric distance; (iii) investigate the role that this turbulence plays in power laws of the magnetic energy spectrum of fluctuations observed by Helios measurements between 0.3 AU and 0.4 AU; and, (iv) establish predictions of the properties of turbulent fluctuations that the PSP will measure. This CAREER investigation is also timely, because it will lay the theoretical and numerical framework needed for interpretation of the PSP signals before the first measurements become available at the end of 2018. The outcome of this research combined with the future PSP observations will not only contribute to expand our knowledge of the fundamentals of Alfvenic turbulence in this region, but will lead to transformative advances towards determining the viability of Alfvenic turbulence as a major mechanism for the heating of the corona and the acceleration of the solar wind.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.