A fluid model is developed for the description of microturbulence and trans
port in magnetized, long mean-free-path plasmas. The model incorporates bot
h electrostatic and magnetic fluctuations, as well as finite Larmor radius
and kinetic effects. Multispecies Landau fluid equations are derived from m
oments of the electromagnetic gyrokinetic equation, using fluid closures wh
ich model kinetic effects. A reduced description of electron dynamics, appr
opriate for the study of microturbulence on characteristic ion drift and Al
fven scales, is derived via an expansion in the electron to ion mass ratio.
The reduced electron equations incorporate curvature, delB, and linear and
nonlinear ExB drift effects, needed to model the electron contribution to
the drive and damping of ion gyroradius scale instabilities in tokamaks. Th
e Landau fluid model is linearly benchmarked against gyrokinetic codes, and
found to reproduce the toroidal finite beta ion temperature gradient and k
inetic ballooning instabilities. (C) 2001 American Institute of Physics.