Emission from extreme astrophysical plasmas: Toward first-principles predictions

Daniel Groselj, Ph.D.

High-energy astrophysical objects, such as neutron stars, accreting black holes, or gamma-ray bursts are behind some of the most exciting recent discoveries in astronomy. Recent highlights include multi-messenger observations of neutrinos from active galaxy cores, the detection of the electromagnetic counterpart of a gravitational wave event, powered by a binary neutron star merger, and the first “image” of a black-hole shadow.

The emission from high-energy sources is produced in hot plasmas far from thermal equilibrium, energized by dissipative processes, such as turbulence, shocks, and magnetic reconnection. These processes have been extensively studied with kinetic particle models and high-performance computer simulations. However, in high-energy sources, matter and radiation can interact through various leptonic and hadronic channels not accounted for in conventional plasma models. This presents new challenges and opportunities for the study of turbulence, shocks and magnetic reconnection under extreme conditions, featuring intense radiation and strong fields.
As an example, I will highlight recent investigations of plasma turbulence in radiatively dense environments near accreting black holes. I will demonstrate that a sufficiently compact and magnetically powered turbulent source can operate as an efficient particle accelerator, while producing X-ray spectra consistent with observations. The method employed here opens a pathway for first-principles predictions of emission from a variety of high-energy sources.

To participate in this event virtually via Zoom, go to https://uiowa.zoom.us/j/91729738002?from=addon.