title: Particle pinch in gyrokinetic simulations of closed field-line systems.
abstract: Gyrokinetic simulations of small-scale turbulent transport in a closed magnetic field-line plasma geometry are presented. The simulations are potentially applicable to dipolar systems such as the levitated dipole experiment (LDX) [J. Kesner, Plasma Phys. Rep. 23, 742 (1997).] and planetary magnetospheres, as well as simpler systems such as the Z pinch. We report here for the first time the existence of a robust particle (and weaker temperature) pinch regime, in which the particles are transported up the density gradient. The particle pinch is driven by non-MHD entropy-mode turbulence at k(⊥) ρ(i) ∼ 1 and particle pinch appears at larger η ≡ L(n)/L(T) ≳ 0.7, consistent with quasilinear theory. Our results suggest that entropy-mode transport will drive the LDX plasma profiles toward a state with η ∼ 0.7 and pressure gradients that are near marginal ideal MHD interchange-mode stability.
authors.affiliation: Department of Physics and Astronomy, Dartmouth College, Hanover, New Hampshire 03755, USA. sumire.kobayashi@dartmouth.edu
authors.forename: Sumire
authors.initials: S
authors.lastname: Kobayashi
authors.forename: Barrett N
authors.initials: BN
authors.lastname: Rogers
authors.forename: William
authors.initials: W
authors.lastname: Dorland