The influence of temperature dynamics and dynamic finite ion Larmor radius effects on seeded high amplitude plasma blobs

TL;DR

This study investigates how temperature dynamics and finite Larmor radius effects influence the behavior of plasma blobs in fusion devices, revealing new scaling laws and the impact on particle transport.

Contribution

It introduces a comprehensive gyrofluid model capturing high fluctuation amplitudes and dynamic finite Larmor radius effects, providing new insights into blob dynamics.

Findings

Maximal radial blob velocity scales with the square root of initial pressure perturbation.

Finite Larmor radius effects lead to highly compact, poloidally propagating blobs.

Empirical scaling laws for blob velocities are established.

Abstract

Thermal effects on the perpendicular convection of seeded pressure blobs in the scrape-off layer of magnetised fusion plasmas are investigated. Our numerical study is based on a four field full-F gyrofluid model, which entails the consistent description of high fluctuation amplitudes and dynamic finite Larmor radius effects. We find that the maximal radial blob velocity increases with the square root of the initial pressure perturbation and that a finite Larmor radius contributes to highly compact blob structures that propagate in the poloidal direction. An extensive parameter study reveals that a smooth transition to this compact blob regime occurs when the finite Larmor radius effect strength, defined by the ratio of the magnetic field aligned component of the ion diamagnetic to the $\vec{E}\times\vec{B}$ vorticity, exceeds unity. The maximal radial blob velocities agree excellently with the inertial velocity scaling law over more than an order of magnitude. We show that the finite Larmor radius effect strength affects the poloidal and total particle transport and present an empirical scaling law for the poloidal and total blob velocities. Distinctions to the blob behaviour in the isothermal limit with constant finite Larmor radius effects are highlighted.