Theory of trapped-particle-induced resistive fluid turbulence

Publisher Website
Google Scholar
Abstract
A theory of anomalous electron heat transport, evolving from trapped‐particle‐induced resistive interchange modes, is proposed. The latter are a new branch of the resistive interchange‐ballooning family of instabilities, destabilized when the pressure carried by the unfavorably drifting trapped particles is sufficiently large to overcome stabilizing contributions coming from favorable average curvature. Expressions for the turbulent heat diffusivity and anomalous electron thermal conductivity at saturation are derived for two regimes of trapped‐particle energy: (i) a moderately energetic regime, which is ‘‘fluidlike’’ in the sense that the unstable mode grows faster than the time that it takes for particles in this energy range to precess once around the torus, and (ii) a highly energetic regime, where the trapped species has sufficiently high energy as to be able to interact resonantly with the mode. Unlike previous theories of anomalous transport, the estimates of diffusion and transport obtained here are self‐consistent since the trapped particles do not ‘‘see’’ the magnetic flutter due to their rapid bounce motion. The theory is valid for moderate electron‐temperature, high ion‐temperature (auxiliary heated) plasmas and as such, is relevant for present‐ and future‐generation experimental fusion devices.