Abstract: Astronomical observations suggest pervasive, dynamically important magnetic fields in our Galaxy and the intracluster medium. Their origin remains a long-standing question in astrophysics and cosmology, with dramatic implications for the evolution of large-scale structures, transport of high-energy cosmic rays, and radiative processes. It is widely believed that such fields first arose as weak 'seeds' generated by cosmic batteries, and were subsequently amplified by the turbulent plasma flows to current levels via the 'dynamo' process -- a fundamental plasma process that converts the mechanical energy of plasma motions into magnetic energy through electromagnetic induction. In this talk, I will provide a unified paradigm for understanding the origin and evolution of cosmic magnetism by taking into account the effects of nonequilibrium micro-physics of collisionless plasmas on macroscopic astrophysical processes. Using analytical theory and first-principles numerical simulations, I demonstrate that the first 'seed' magnetic fields can spontaneously emerge under generic turbulent motions through kinetic plasma instabilities, and the cosmic plasmas are thus ubiquitously magnetized. The cross-scale, nonlinear coupling between the microscopic magnetic fields and the macroscopic flow enhances the turbulence and accelerates the plasma dynamo. The magnetic field is therefore amplified rapidly until it reaches energy equipartition with the turbulent flow. The ab initio production of these equipartition fields from an unmagnetized plasma through astrophysical turbulence advances a fully self-consistent and predictive explanation of the prevalence of cosmic magnetism --- a key goal of upcoming radio telescopes such as the Square Kilometer Array.
***Join before the Colloquium at 3:00 pm for coffee, cookies and brownies from Lou's in Wilder 103!***
Hosted by Professor Yi-Hsin Liu
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