Collaborative Research: Electron Acceleration and Emissions from the Solar Flare Termination Shock

这个合作研究项目计划在我们对太阳物理学的一个关键问题的理解上取得重大进展；也就是说，电子是如何在太阳耀斑中加速的问题。太阳耀斑是太阳系中最强烈的爆炸，它们为粒子加速和高能发射提供了场所。然而，这种加速究竟是如何发生的问题仍未得到解决。该项目将结合两个强大的数值模型，使主要研究人员（pi）能够在大范围内模拟物理，从产生冲击波的大规模耀斑到粒子加速发生的最小尺度。该项目还将支持下一代太阳科学家的培训。该项目将包括本科生和研究生，并为该项目的博士后研究员提供资金。在太阳耀斑中，当耀斑的高速流出物遇到太阳大气中的磁环时，就会形成一个能将粒子加速到高能量的驻波，从而产生终止激波。这些冲击波已经被预测到，但直到最近由一个pi进行的x射线和射电观测（Chen）才被观测到。受这一最新发现的启发，该项目计划通过首次结合两种强大的数值模拟来研究终止激波的动态演化及其电子加速度：(1)耀斑动态演化的大规模磁流体动力学（MHD）模型，以及(2)激波前沿电子加速的细胞内粒子动力学和测试粒子模拟。从组合的数值模型中，pi计划产生合成的硬x射线发射，并将其与观测结果进行比较。

This collaborative research project plans to make significant progress toward our understanding of one of the key problems in solar physics; i.e., the question of how electrons are accelerated within solar flares. Solar flares are the strongest explosions in the Solar System, and they provide sites for particle acceleration and high-energy emission. However, the question of exactly how this acceleration occurs remains unsolved. The project will combine two powerful numerical models that will enable the principal investigators (PIs) to simulate the physics over a wide range of scales from the large scale flares that produce shock waves down to the smallest scales where the particle acceleration occurs. This project will also support the training of the next generation of solar scientists. The PIs will involve both undergraduate and graduate students in the research, and funding is provided for a postdoctoral researcher for the project.In solar flares, a termination shock can develop when a high-speed outflow from the flare encounters magnetic loops in the solar atmosphere forming a standing shock wave that can accelerate particles to high energies. These shock waves had been predicted but never observed until recent X-ray and radio observations by one of the PIs (Chen). Motivated by this recent discovery, this project plans to investigate the dynamical evolution of termination shocks and their acceleration of electrons by combining, for the first time, two powerful numerical simulations: (1) large-scale magnetohydrodynamic (MHD) models of the dynamical evolution of a flare and (2) particle-in-cell kinetic and test-particle simulations for electron acceleration at the shock front. From the combined numerical model the PIs plan to generate synthetic hard X-ray emission and compare this emission with observations.