Speaker: Professor Steven Cowley, Princeton Plasma Physics Laboratory
Abstract: Magnetized plasmas—whether in nature or in the laboratory—often undergo sudden, dramatic eruptions that release large amounts of energy and disrupt confinement. Edge localized modes (ELMs) in Tokamaks are a good example. Why some plasmas erupt while others remain limited by turbulence is still not fully understood. In this talk, I will examine the instability mechanisms that drive eruptive behavior and show that many plasmas are metastable, i.e. stable to small perturbations but unstable to large perturbations. When triggered, this metastable state can lead to explosive events. I will highlight how this phenomenon manifests in both edge localized modes in fusion devices and in solar flares. Following such eruptions, the plasma must settle into a new equilibrium. I will present key examples where these relaxed equilibrium states can be calculated accurately.