Speaker: Dr. Christopher Bambic

Host: Prof. John Wise

Title: Coronal Heating and Feedback from Luminous Accretion Flows: Challenges and Insights from Local and Global Simulations

Abstract

Radiatively efficient accretion represents a frontier problem for computational astrophysics. Through leveraging GPU acceleration and exascale supercomputer architectures, the H-AMR Collaboration, led out of Georgia Tech, has been working to understand the structure of accretion flows onto black holes, where strong magnetic fields, two-temperature plasma physics, radiation transport, and general relativity may all imprint themselves on the radiative and kinetic feedback observed from black-hole-powered sources. In this talk, I will discuss our ongoing efforts to model accretion flows across a wide range of accretion rates, from the radiatively inefficient regime powering targets of the Event Horizon Telescope, to the super-Eddington regime, which may be relevant for sources such as tidal disruption events, ultra-luminous X-ray sources, and quasars. Special attention is given to the thin-disk regime at around 1 to a few tens of percent of the Eddington limit, where hard X-ray emission, thought to emerge from a hot (billions of Kelvin) "corona," is routinely observed. I will discuss two different models for the coronal geometry, the "sandwich" and "truncated disk" models, and what we have learned about possible coronal heating mechanisms based both on the local stratified shearing-box calculations I explored during my Ph.D., and the especially high-resolution global simulations that I have been exploring here at Tech.