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关键问题之一的理解方面取得重大进展;即，电子在太阳耀斑中是如何被加速的 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然没有解决。 该项目将结合联合收割机两个强大的数值模型，使主要研究人员（PI）能够模拟从产生冲击波的大尺度耀斑到粒子加速发生的最小尺度的物理学。 该项目还将支持培训下一代太阳科学家。 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，会形成一个可以将粒子加速到高能量的驻波，从而产生终止激波。 这些冲击波曾被预测过，但从未被观测到，直到最近的X射线和无线电观测的一个PI（陈）。 受这一最新发现的启发，该项目计划首次结合两个强大的数值模拟来研究终止激波的动力学演化及其对电子的加速：（1）耀斑动力学演化的大尺度磁流体动力学（MHD）模型和（2）激波前沿电子加速的粒子动力学和测试粒子模拟。 PI计划根据组合的数值模型生成合成硬X射线发射，并将该发射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.