The Naval Research Laboratory (NRL) high-latitude ionosphere-magnetosphere mesoscale coupling model has been used to develop constraints on and scaling laws associated with the spectrum of interchange-like instabilities and processes believed to be operating in the high-latitude ionosphere. In this model, current closure in the ionospehre is given by Pedersen currents, while in the magnetophere, closure is achieved with polarization currents. For Pedersen current-driven interchange-like instabilities with growth rate &ggr;, we treat the limit &ngr;<&ggr;, where &ngr; is the ion collision frequency averaged over a flux tube. The spectrum scaling laws for interchange-like instabilities are developed using conservation laws implied by the fundamental nonlinear equations contained in the NRL coupling model. For the density spectrum implied by the interchange instability in the high-latitude ionosphere we solve for the spectral index and develop scaling relationships for the outer scale with ambient ionospheric quantities. For density spectrum of the form (1+(k/k0)2)-n/2 we show that 1<n<3 in the steady state regime, where k is wave number perpendicular to the magnetic field and k0 is the outer scale wave number. The bounds on the spectral indices as predicted by the approach are shown to be consistent with experimental observations. Applications to mesoscale dynamics, structure, and stability of convecting inhomogeneities and large-scale plasma density structures in the high-latitude ionosphere have been made. ¿American Geophysical Union 1990