  Drift instabilities contribute to the formation of edge turbulence and zonal
flows, and thus the anomalous transport in tokamaks. Experiments often found
micro-scale tur- bulence strongly coupled with large-scale magnetohydrodynamic
(MHD) processes, whereas a general framework has been lacking that can cover
both regimes, in partic- ular, their coupling. In this paper, the linear
resistive drift wave instability (DWI) is investigated using a full 2-fluid MHD
model, as well as its numerical implementation in NIMROD code. Both analytical
and numerical analyses reveal a macro-scale global drift wave eigenmode coupled
with MHD dynamics and illustrate a non-monotonic dispersion relation with
respect to both perpendicular and parallel wavenumbers. NIMROD results also
reveal an edge-localized behavior in the radial mode structure as the azimuthal
mode number increases, implying the dependence of the 2-fluid ef- fects due to
the inhomogeneous density profile. The edge-localization introduces a
non-trivial dependence of the effective perpendicular wavenumber to the
perpendicular mode number, which may explain the quantitative difference
between the global dispersion relation and its local approximation from the
conventional local theory.
