This project will investigate the two-dimensional spatial distribution of plasma irregularity structures in the F-region ionosphere and their relationship to the development of density perturbations known as equatorial spread-F (ESF).  Better understanding of such ionospheric disturbances and their generation is highly relevant to radio wave propagation, scintillations, and communication and navigation applications. The project will obtain a new set of interferometric radar images of F-region irregularities and analyze them to determine the spatial distribution of scattering structures within the radar beam, to identify  patterns or periodicities related to underlying plasma waves, and to quantify the correlation between ESF structures and clusters of bottom-type irregularities. The project will fine-tune an interferometric system to study scattering structures with zonal scale sizes of several kilometers or more, and the project will focus on structures having scale sizes less than a few tens of km, for which few investigations have been conducted to date.