Nonpotential waves in the auroral electrojet

An ionospheric plasma instability in the auroral electrojet region, believed to be responsible for electromagnetic waves with angular frequency omega smaller than nu sub(i) is discussed. The threshold current velocity U sub(t) and oscillation growth rate gamma are found for the realistic physical situation when a nonuniform plasma density and an ionization function are considered. It is found that the gradient of plasma density Delta n may be neglected in the expressions for U sub(t) and gamma , and that the spectral density of fluctuations in the density of the plasma agrees with the experimental data.