  Progress in understanding the coupling between plasma instabilities in the
equatorial electrojet based on a unified fluid model is reported. A deeper
understanding of the linear and nonlinear evolution and the coupling of the
gradient-drift and Farley-Buneman instabilities is achieved by studying the
effect of different combinations of the density-gradient scale-lengths (Ln) and
cross-field (E?B) drifts on the plasma turbulence. Mechanisms and channels of
energy transfer are illucidated for these multiscale instabilities. Energy for
the unified model is examined, including the injected, conservative
redistribution (between fields and scales), and ultimate dissipation. Various
physical mechanisms involved in the energetics are categorized as sources,
sinks, nonlinear transfer, and coupling to show that the system satisfies the
fundamental law of energy Oonservation. The physics of the nonlinear transfer
terms is studied to identify their roles in producing energy cascades { the
transference of energy from the dominant unstable wavenumbers and driving
irregularities of different scale-lengths. The theory of two-step energy
cascading to generate the 3-meter plasma irregularities in the equatorial
electrojet is verified. In addition, the nonlinearity of the system allows the
possibility for a reverse energy cascading, responsible for generating
large-scale plasma structures at the top of the electrojet.

Plasma Physics