The Physics of Cold-Hot Interfaces in the Multiphase Circumgalactic Medium

Wednesday Sep 16, 2026, 2:00 PM → 3:00 PM Asia/Shanghai

Tsung-Dao Lee Institute/S4F-SW - Open Area (Tsung-Dao Lee Institute)

Suoqing（索清） Ji（季）

Host: Mengtao Tang
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Abstract：
The circumgalactic medium (CGM) is a dynamic, multiphase environment where cool gas, hot plasma, and galactic outflows interact across a wide range of scales. The interfaces between these phases play a central role in regulating mass, momentum, and energy exchange, and therefore provide a key link between small-scale gas physics and galaxy-scale feedback. I will first give a brief overview of the multiphase CGM and its connection to galactic feedback. I will then discuss the physics of turbulent mixing layers, with particular emphasis on charge exchange as a potential probe of otherwise difficult-to-observe cold-hot interfaces. Finally, I will introduce the conditional nonlinear optimal perturbation method as a new approach to identifying the perturbations that produce the strongest nonlinear growth at cold-hot interfaces, with broader implications for understanding nonlinear instabilities in astrophysical systems.

Biography:
Dr. Suoqing Ji is an assistant professor at the Center for Astronomy & Astrophysics and the Physics Department, Fudan University. He obtained his Ph.D. in physics from University of California Santa Barbara in 2018, and then worked at Caltech as a Sherman Fairchild Prize Fellow in theoretical astrophysics from 2018 to 2021. His research interests include magnetohydrodynamics, turbulence, hydrodynamic and thermal instabilities, cosmic rays, etc., and their application in galactic and stellar physics.