Collaborative Research: NSF-BSF: Influence of Upstream Turbulence and Shock Rippling on Downstream Relaxation in Collisionless Shocks

About This Grant

This award supports a collaborative research effort by the Space Science Institute, the University of Alabama in Huntsville, and Ben-Gurion University in Israel. The main goal of the project is to understand fundamental properties of shock waves in astrophysical plasmas. Shocks are strong disturbances that may occur when objects move through a medium with very large speed. Plasma shocks are very important phenomena because they can efficiently convert flow energy into heat and acceleration of individual particles to high energies. For example, shocks produced by astrophysical explosions are thought to operate as giant particle accelerators, producing some of the most energetic particles in the Universe. Similarly, a shock standing in front of the Earth slows down the solar wind, a stream of plasma coming from the Sun. As a result, this shock plays an important role in controlling space weather, understanding which is essential for protecting critical communication and navigation satellites, as well as power grids here on Earth. This project will use a combination of computer simulations, analytical theory, and spacecraft observations to uncover a relation between properties of the shocks and the heating and acceleration of plasma behind the shock. The project outcomes will inform a wide variety of investigations, including studies of space weather. Concurrently with advancing the fundamental science of plasma shocks, the award supports several educational and outreach efforts for university and K-12 students. Collisionless shocks are some of the most ubiquitous strongly nonlinear phenomena in space and astrophysical plasmas. They rapidly convert energy of the upstream flow into heating, acceleration of particles to high energies, and magnetic field generation. Relaxation and self-organization processes behind the shock have a strong impact on the overall energy partition and may determine the coupling of the shock to the host system. This study will advance the understanding of how the time-dependent shock rippling, accompanied by plasma instabilities and turbulence, provides necessary relaxation of the plasma to a self-organized state with a high energy particle population. This will be accomplished using a combination of theoretical and numerical kinetic modeling combined with observational data analysis, with the study of energetic particle acceleration in collisionless astrophysical shocks contributing to the goals of NSF's "Windows on the Universe: The Era of Multi-Messenger Astrophysics" meta-program. The project outcomes are expected to impact understanding of many geospace and astrophysical systems, including studies of the Earth’s magnetosheath and its dynamical magnetopause, shock waves associated with coronal mass ejections, and of their geomagnetic effects. Through training of students, postdocs, and early-career scientists, the project will promote education in computational science and plasma physics. 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.