A simple nonlinear equation is derived to describe the pseudo‐three‐dimensional dynamics of a nonuniform magnetized plasma withTe≫Tiby taking into account the three‐dimensional electron, but two‐dimensional ion dynamics in the direction perpendicular toB0. The equation bears a close resemblance to the two‐dimensional Navier–Stokes equation. A stationary spectrum in the frequency range of drift waves is obtained using this equation by assuming a coexisting large amplitude long wavelength mode. The &ohgr;‐integratedkspectrum is given byk1.8(1+k2)−2.2, while the width of the frequency spectrum is proportional tok3(1+k2)−1, wherekis normalized bycs/&ohgr;ci. The result compares well with the recently observed spectrum in the ATC tokamak.