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。该任务计划于2018年夏天发射，将访问以前从未有任何航天器探索过的近太阳区域，提供开创性的在9.5到55太阳半径（从太阳中心测量）之间的内日球层的原位和近距离遥感测量，比太阳神任务近6倍。这个为期五年的CAREER项目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上层大气的，以及这些能量是如何消散以加热日冕并加速太阳风的。该项目的主要影响之一是，它将通过为解释PSP测量结果奠定理论基础，从而提高PSP任务的科学回报，这将对日球层物理学中许多其他悬而未决的问题产生影响。该项目团队将引入一种新颖且用户友好的软件工具，允许学生在最少的科学计算知识的情况下使用数值模拟，以加强对入门空间等离子体物理学的学习。数值模拟在入门课程中所扮演的角色将与模拟在现代等离子体研究中所扮演的角色密切相关，即，当分析进展不再可能时，促进对基础物理的理解。软件界面将允许学生快速解决数值问题，从数值解决中获得直觉，以帮助加强对潜在概念的理解。这个项目的另一个主要的更广泛的影响是，在它的结论，这个工具的一个完整的测试和工作版本将在GNU开源许可证下在线提供，允许扩展其等离子体物理问题库并在其他研究机构中使用。这一软件工具也将被用于向公众传播该项目的研究成果，并向他们介绍空间等离子体研究的相关性以及PSP将在未来几十年实现的革命性发现。该CAREER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CAREER预计将提供对近太阳环境中湍流的起源和演化的更好理解，从低日冕观测到的阿尔芬波到上日冕和太阳风的湍流波动。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前所未有的测量奠定基础。该项目旨在实现以下具体的科学目标：(i)研究湍流如何从日冕的AW运动演变为更大日心距离上充分发展的AW湍流；（ii）确定控制惯性范围功率谱的标度规律，交叉螺旋度和剩余能量在湍流中的作用，以及这些特性如何依赖于日心距离；（iii）研究这种湍流在太阳神号在0.3天文单位和0.4天文单位之间测量观测到的波动的磁能谱幂律中所起的作用；（iv）建立对PSP将要测量的湍流波动特性的预测。这次CAREER调查也很及时，因为它将在2018年底第一次测量可用之前为解释PSP信号奠定理论和数值框架。这项研究的结果与未来的PSP观测相结合，不仅有助于扩大我们对该地区阿尔芬尼湍流基本原理的认识，而且将在确定阿尔芬尼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重大进展。该奖项反映了美国国家科学基金会的法定使命，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。

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.