Energy-conserving Finite-beta Electromagnetic Drift-fluid Equations

Nonlinear energy-conserving drift-fluid equations that are suitable to describe self-consistent finite-beta low-frequency electromagnetic (drift-Alfven) turbulent fluctuations in a nonuniform, anisotropic, magnetized plasma are derived from a variational principle. The variational principle is based on a drift-fluid Lagrangian that contains linear and nonlinear E x B velocities derived directly from the corresponding single-particle finite-beta gyrocenter Hamiltonian (in the zero-Larmor-radius limit). Covariant electromagnetic effects introduce a magnetic generalization to the standard ion polarization density as well as introduce a new ion magnetization current, which are both missing from existing gyrofluid and drift-fluid Poisson-Ampere equations. An exact energy conservation law is also derived directly from the drift-fluid Lagrangian by application of the Noether method.