Extension of Landau-fluid closure to weakly collisional plasma regime

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Both collisionless and collisional Landau fluid (LF) closure have been developed and implemented in two-fluid plasma simulation framework BOUT++, taking full advantage of the fast non-Fourier method (Dimits, 2014). The spectral range of good fit can be conveniently extended to larger domain by adding more Lorentzians. The scaling for upper limit of wavenumber resolved in collisionless LF operator and the fitting coefficients for the collisional LF operator, the later is extended to weakly collisional regime (νe∗∼0.01), are presented in this paper. The flux limited expression q∥eFL is reduced to free streaming expression q∥eFS in collisionless limit and gives classical Spitzer–Härm result q∥eSH in collisional limit as we expected. The collisional LF closure recovers the classical Spitzer–Härm result q∥eSH in collisional limit and is same as the collisionless LF closure in collisionless limit. The test cases also obviously demonstrate the nonlocal effects from LF closures and responding to different boundary conditions in open surface region. This work will make it more applicable and possible to include the Landau damping kinetic effect in the fluid simulation of tokamak plasma.