The E × B staircase of magnetised plasmas

Abstract

We show that a class of near-marginal and low-collisional magnetised plasmas naturally evolve into a globally organised state dubbed the ' × E B staircase'. A key signature of this self-organised state is the containment of avalanche activity, detrimental for confinement, by a series of microbarriers for transport, the staircase steps, beneficial for confinement. Conditions for existence of the × E B staircase, impact on transport and confinement and robustness in parameter space are discussed.

Lévy flights on a comb and the plasma staircase

“…This gives rise to some features of bifurcation, which might be identifiable in the experiment. This observation opens a new perspective on "smart" plasma diagnostics in tokamaks using plasma self-organization [1][2][3].…”

Evidence for Global Edge–Core Interplay in Fusion Plasmas

“…Whilst a submarginal state may exist globally, a regime of near-marginality is frequently inhomogeneous in time and in space, displaying a range of transport properties [9] as submarginal and turbulent patches coexist, with intermittent behaviour. Global-scale organisation of turbulence, from core (ρ = r/a 0.6) to edge (0.9 ρ 1) is here investigated in such regimes, in the relevant low-heating limit of flux-driven forcing and using the gyrokinetic approach in Gysela [10,11].Gysela has recently been upgraded to account beyond the outer edge for SOL-like (ρ ≥ 1) boundary conditions [12]. A sink is progressively added from ρ = 1.05 to 1.15 author's e-mail: guilhem.dif-pradalier@cea.fr * ) This article is based on the invited talk at the 33rd JSPF Annual Meeting (2016, Tohoku).…”

“…Gysela has recently been upgraded to account beyond the outer edge for SOL-like (ρ ≥ 1) boundary conditions [12]. A sink is progressively added from ρ = 1.05 to 1.15 author's e-mail: guilhem.dif-pradalier@cea.fr * ) This article is based on the invited talk at the 33rd JSPF Annual Meeting (2016, Tohoku).…”

“…Gysela has recently been upgraded to account beyond the outer edge for SOL-like (ρ ≥ 1) boundary conditions [12]. A sink is progressively added from ρ = by enforcing exponentially-decaying density and temperature profiles.…”

“…The usual fluxgradient paradigm [21] bijectively relates the local values for fluxes to the local values of the gradients. In fluxdriven approaches this paradigm is challenged [5,9,12] as both fluxes and profiles evolve consistently and are unknown functions of the dynamics. The flux-gradient relation thus evolves in time, may become multivalued (different gradient drives may be associated to the same flux) and consequently non monotonic (a larger gradient drive may be associated to a lower flux).…”