Padé-based arbitrary wavelength polarization closures for full-F gyro-kinetic and -fluid models

Abstract

We propose a solution to the long-standing long wavelength polarization closure shortfall of full-F gyro-fluid models. This is achieved by first finding an appropriate quadratic form of the gyro-fluid moment over the second order Hamiltonian. Secondly, we deduce Padé-based approximations to the latter expression, that produce a polarization charge density with the opted order of accuracy and mimic linear polarization effects for arbitrary wavelengths. The proposed closures feature proper energy conservation and the anticipated Oberbeck-Boussinesq and long wavelength limit.