Dr. Rogério Jorge, École Polytechnique Fédérale De Lausanne, (Switzerland)

"A gyrokinetic model for the tokamak periphery"

Abstract: We present a new gyrokinetic model that retains the fundamental elements of the plasma dynamics at the tokamak periphery, namely electromagnetic fluctuations at all scales, comparable amplitudes of background and fluctuating components, and a large range of collisionality regimes. Such model is derived within a gyrokinetic full-F approach, describing distribution functions arbitrarily far from equilibrium, and projecting the gyrokinetic equation onto a Hermite-Laguerre velocity space polynomial basis, obtaining a gyrokinetic moment hierarchy. The treatment of arbitrary collisionalities is performed by expressing the full Coulomb collision operator in gyrocentre phase space coordinates, and providing a closed formula for its gyroaverage in terms of the gyrokinetic moments. In the electrostatic regime and long-wavelength limit, the novel gyrokinetic hierarchy reduces to a drift-kinetic moment hierarchy that in the high collisionality regime further reduces to an improved set of drift-reduced Braginskii equations, which are widely used in scrape-off layer simulations. First insights on the linear modes described by our novel gyrokinetic model will be presented.