Ionospheric Irregularities: Frontiers

Contemporary research into modeling plasma density irregularities and the ionospheric instabilities responsible for them is reviewed. Three classes of waves are singled out for detailed examination. These include gradient drift and Farley-Buneman waves in the equatorial electrojet, collisional interchange instabilities associated with equatorial spread F (ESF), and resistive drift waves, which may be responsible for irregularities in midlatitude sporadic E layers. Three cross-cutting themes drive the analyses. One of these concerns the shortcomings of the oftenmade equipotential magnetic field line assumption. Another is the role of stochastic forcing in shaping wave behavior, motivated by an overview of stochastic differential equation formalism. The third is the necessity of initial-value analysis for large-scale waves in inhomogeneous flows. The themes are illustrated by analysis and numerical simulations of E and F region ionospheric instabilities.