Inertial blob-hole symmetry breaking in magnetised plasma filaments

TL;DR

This study uses advanced gyrofluid simulations to explore how inertia influences the asymmetric propagation of plasma filaments, revealing conditions under which blobs and holes accelerate or slow down, impacting plasma confinement.

Contribution

It demonstrates the role of finite inertia effects in symmetry breaking between plasma blobs and holes, with implications for edge plasma behavior in tokamaks.

Findings

Blobs propagate slower than holes on flat density backgrounds.

Large density gradients reverse the propagation speed asymmetry.

Blob turbulence spreads vorticity rapidly, holes remain coherent longer.

Abstract

Symmetry breaking between the propagation velocities of magnetised plasma filaments with large positive (blob) and negative (hole) amplitudes, as implied by a dimensional analysis scaling, is studied with global ("full-n") non-Boussinesq gyrofluid computations, which include finite inertia effects through nonlinear polarisation. Interchange blobs on a flat density background have higher inertia and propagate more slowly than holes. In the presence of a large enough density gradient, the effect is reversed: blobs accelerate down the gradient and holes are slowed in their propagation up the gradient. Drift wave blobs spread their initial vorticity rapidly into a fully developed turbulent state, whereas primary holes can remain coherent for many eddy turnover times. The results bear implications for plasma edge zonal flow evolution and tokamak scrape-off-layer transport.