CCA Colloquium: Gregory G. Howes

Title: Developing Predictive Models of Turbulent Heating in Space and Astrophysical Plasmas

Abstract: Predictive models of turbulent plasma heating are essential for the interpretation of remote astronomical observations of emissions from black hole accretion disks, such as the ground-breaking observations by the Event Horizon Telescope of the supermassive black holes at the center of M87 and at Sagittarius A* in the Milky Way. Turbulence plays an essential role in space and astrophysical plasmas by mediating the transport of the energy in large-scale magnetic fields and plasma flows down to smaller scales, where poorly constrained physical mechanisms damp the turbulent fluctuations and thereby energize the plasma particles, yielding either the heating of the plasma species or the acceleration of a small fraction of particles to high energy. Predicting the heating or acceleration of the different plasma species by turbulence, based on the observable turbulence and plasma parameters at large scales, is recognized as a grand challenge problem in heliophysics and astrophysics. Through the newly developed field-particle correlation technique, both kinetic numerical simulations andin situspacecraft measurements of weakly collisional plasma turbulence can be used to identify the mechanisms governing the dissipation of plasma turbulence and to quantify the resulting partitioning of energy among the different plasma species. I will cover recent achievements in a long-term program to identify the dominant physical mechanisms controlling the damping of plasma turbulence as a function of the plasma and turbulence parameters. The ultimate goal is to develop turbulent heating prescriptions that can be used in global modeling of astrophysical systems to predict the transport of energy and its impact on system evolution.