Landau-fluid closure and drift-wave dispersion relations for arbitrary collisional plasmas*

The Landau fluid model has been revisited to describe drift-wave instabilities in edge plasmas where the plasma parameters can vary by an order of magnitude or more. Usually, simple fluid models without Landau-fluid closure have been used to describe edge plasma dynamics. However, the collisionality conditions for the simple fluid descriptions are only marginally satisfied in present-day tokamaks and the validity conditions for such models will not be satisfied for future devices. As a result, the simple fluid models without Landau closure cannot properly describe the electron kinetic effects (e.g. the wave-electron resonances) in weakly collisional plasmas. We compare the analytical growth rates of drift-wave instabilities from the electromagnetic Landau-fluid model and the electromagnetic drift-kinetic model by conducting linear analysis on both models in various plasma parameters. Consequently, we demonstrate that both the electromagnetic Landau-fluid model and the electromagnetic drift-kinetic model, which yield similar linear growth rates, can be used to describe drift wave turbulence in a wide range of plasma parameters. We also present comparative simulations of drift wave instability using BOUT++ and COGENT(M. Dorf, invited talk, this meeting).