  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.
