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

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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.