CAREER: A Novel and Fast Open-Source Code for Global Simulation of Stratified Convection and Magnetohydrodynamics of the Sun

非技术：该项目的目标是创造一种预测太阳密度分层磁流体动力学的独特能力。这项研究预计将为开发预测极端空间天气的方法奠定基础，例如极端地磁风暴之后的“超级太阳耀斑”事件。这项研究的科学结果可以帮助解决以前对太阳对流区的研究中一些相互矛盾的预测。首席研究员（PI）将开发和传播一个强大的开源软件包，以空间天气和太阳物理社区。对恶劣空间天气事件的成功预测具有重大的社会和经济影响。PI将设计高阶精确的计算算法，适用于每秒可以执行十亿次计算的百亿亿次模拟。该软件将在大规模并行分布式存储计算机上运行，以预测太阳的全局和局部耦合动态。PI将接触到K-12的学生，并证明太阳科学和高性能计算对社会是令人兴奋和重要的。此外，PI将利用与国家大气研究中心高空观测站和其他研究中心的外展努力。因此，这个项目符合美国国家科学基金会的使命：促进科学进步，促进国家福利。技术：这项研究计划的目标是开发一种新颖的、完全可压缩的模型和一个开源社区代码，用于太阳对流区（包括太阳近表面切变层的顶部）的全球模拟。目前领先的全球模拟使用弹性近似，其计算域从太阳对流区底部延伸，必须停止在约0.96太阳半径处，停止在马赫数可以达到统一的近地表切变层的顶部。本研究计划将创建一个强大的开源社区代码CHORUS++来模拟太阳对流区的磁流体动力学。CHORUS是可压缩的高阶非结构网格谱差码，是由PI共同开发的用于太阳对流区流体力学的谱差码。CHORUS++将配备可变网格分辨率能力，以聚焦目标区域。为了在大规模并行计算机上进行长时间积分，将为CHORUS++设计并装备一种快速局部时间步进算法。这些技术成就可以将原始CHORUS代码的速度提高100倍以上。PI将以前所未有的分辨率对太阳对流区的磁流体动力学进行一系列全球模拟，以预测太阳的微分旋转、经向环流、巨细胞和超粒化。

Non-technical: The goal of this project is to create a unique capability for predicting density-stratified magnetohydrodynamics of the Sun. This research is expected to lay a foundation for developing methods for predicting extreme space weather, e.g. the event of a "super solar flare" followed by an extreme geomagnetic storm. Scientific results of this research can help resolve several contradictory predictions from previous studies of the solar convection zone. The Principal Investigator (PI) will develop and disseminate a powerful open-source software package to the space weather and solar physics communities. The success of predicting severe space weather events has significant societal and economic impacts. PI will design high-order accurate computational algorithms suitable for exascale simulations that can perform a billion billion calculations per second. This software will run on massively parallel distributed-memory computers to predict coupled global and local dynamics of the sun. PI will reach out to K-12 students and demonstrate that science of the sun and high-performance computing are exciting and important to society. Furthermore, PI will leverage outreach efforts with the High Altitude Observatory of the National Center for Atmospheric Research and other research centers. This project, thus, serves the national interest as stated by NSF's mission: to promote the progress of science and to advance the national welfare.Technical: The goal of this research program is to develop a novel, fully compressible model and an open-source community code for global simulations of the solar convection zone that includes the top near surface shear layer of the Sun. Current leading global simulations use an elastic approximation whose computational domains extend from the base of the solar convection zone and must stop at about 0.96 solar radius, stopping short of the top near surface shear layer where Mach number could reach unity. This research program will create a powerful open-source community code CHORUS++ to simulate magnetohydrodynamics of the solar convection zone. CHORUS stands for Compressible High-ORder Unstructured-grid Spectral difference code which has been co-developed by the PI for hydrodynamics of the solar convection zone. CHORUS++ will be equipped with variable mesh resolution capability to focus on targeted regions of interests. A fast local time-stepping algorithm will be designed and equipped for CHORUS++ for long-period time integration on massively parallel computers. These technical accomplishments can accelerate the original CHORUS code by a factor over 100. The PI will conduct a series of global simulations of magnetohydrodynamics of the solar convection zone with unprecedented resolutions for predicting the differential rotation, meridional circulation, giant cells, and super-granulation of the sun.