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Accueil > Séminaires et conférences > Séminaires, soutenances de thèses et HDR précédents > 2012 > Séminaires 2012 > Le mardi 20 mars 2012

## Le mardi 20 mars 2012

Sumire Kobayashi (Department of Physics and Astronomy, Dartmouth College, NH, U.S.A.)

"Particle Pinch in Gyrokinetic Simulations of Closed Field-line Systems"

Saint-Maur, salle de réunion

Gyrokinetic GS2 simulations of plasma turbulence and particle and heat
transport in a dipole magnetic field geometry created by a ring
current are presented. This study is relevant to the MIT/Columbia
University Levitated Dipole Experiment (LDX) [Kesner et al, Plasma
Phys. Reports, 1997], a fusion experiment designed to explore hot
plasma confinement in a dipolar magnetic field. The work also has
potential applications to planetary magnetospheres. In addition to
magnetohydrodynamic (MHD) ideal interchange and ballooning modes, a
non-MHD mode known as the entropy mode is present in this system. The
entropy mode has a scale length smaller than ideal modes ($k_\perp \rho_i \sim 1$) but comparable growth rates. Considering parameter
regimes that are ideally stable, we explore the physics of turbulent
transport generated by entropy modes, finding enormous variation in
the nonlinear dynamics as a function of the density and temperature
gradients. In particular, we report here the existence a new particle
pinch regime, in which the particles are transported up the density
gradient. We show that this discovery is consistent with gyrokinetic
and two-fluid quasi-linear theory. The presence of a particle pinch
appears to be consistent with recent observations in LDX [Boxer et al,
Nature Physics, 2010].

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