Collaborative Research: Decay and Diffusion of Dynamo-Generated Magnetic Fields in Astrophysical Plasmas

About This Grant

This award supports a collaboration between Princeton University and Dartmouth College to explore how self-generated magnetic fields can persist and disperse in turbulent astrophysical plasmas. Astronomical observations of our Galaxy and clusters of galaxies indicate ubiquitous cosmic magnetic fields at the micro-Gauss level, or about one-millionth of the Earth's magnetic field. While weak, such magnetic fields appear to be pervasive and are dynamically important in the Universe even though astrophysical sources of magnetic field generation are often neither steady nor persistent. This collaborative project will use theoretical and numerical modeling approaches to address how present-day galaxies and galaxy clusters not only came to host dynamically important magnetic fields, but also maintain those fields. Such study of the sustenance and longevity of magnetic fields in a turbulent plasma constitutes a key research frontier in plasma astrophysics and basic plasma science. The award will also support an ongoing program of biennial summer schools on plasma astrophysics and astrophysical fluid dynamics for undergraduate and early graduate students. These schools enhance the infrastructure for plasma science research and education in the US by attempting to remedy the relative lack of fluid and plasma physics education in US physics and astronomy curricula. This project will use a combination of analytical theory and a suite of cutting-edge fluid-based and kinetic numerical simulation models to elucidate the decay and diffusion of dynamo-generated magnetic fields in a plasma. The models will take into consideration topological and physical constraints related to magnetic helicity, the plasma particles' adiabatic invariants, and kinetic plasma micro-instabilities. The ultimate goal of this project is to be able to predict the decay laws and the final relaxed state of the magnetic field, including their dependence on the material properties of the plasma. The project will also investigate how magnetic fields that are expelled from spatially localized astrophysical bodies into the intergalactic or intracluster medium subsequently disperse spatially and become volume-filling, and how the kinetic micro-physics of such weakly collisional plasmas helps or hinders this process. This collaborative project will train three graduate students across the two institutions in plasma physics, theoretical astrophysics, and scientific computing, aiding the development of a globally competitive STEM workforce in the US. 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.