Theory of Kilometric Gradient-Drift Structures in the Daytime and Nightime Equatorial Electrojet

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This proposal includes a thorough exploration of the linear instability spectrum, using both eigenmode and initial-value methods, and the two dimensional turbulence that results from the nonlinear growth of these instabilities. The PI will use measured density and electric field profiles. He will attempt to clarify the role of short-wavelength instabilities in the presence of dominant kilometer-scale structures, the distinctions in turbulent characteristics between the upper electrojet in daytime as well as nighttime. Finally, he will ascertain (1) the role of velocity shear, much more effective in damping short-wavelength instabilities than long-wavelength ones, and (2) the self- regulatory role of velocity shear, not only driven by the ambient electric fields and neutral wind, but also possibly generated by a dynamo effect due to the turbulent Reynolds stress at short wavelengths.***