Incoherent and coherent scatter radar studies of the equatorial F region

Abstract

Radio waves are weakly scattered by thermal fluctuations in the quasiequilibrium ionospheric plasma. Coherent scatter echoes, meanwhile, are caused by non-thermal electron density fluctuations generated by plasma instabilities and are much stronger than incoherent scatter (IS) echoes. The spectra of IS echoes provide information about parameters of the background plasma such as electron density, temperatures, and ion composition. On the other hand, coherent scatter echoes provide an indication of the turbulent state of the ionospheric plasma. This dissertation describes coherent and incoherent backscatter radar observations of the F region ionosphere in the magnetic equatorial region using the Jicamarca IS radar in Peru and the Sao Lu ˜ ´ıs coherent backscatter radar in Brazil. The possibility of an alternative IS radar technique for topside ionosphere observations was investigated, and traditional IS techniques were revisited in an attempt to improve electron density observations made at the Jicamarca Radio Observatory. Also, new measurements made with the radar in Brazil are presented which provide additional evidence of plasma waves predicted by a recently proposed theory. Overall, the results in this dissertation provide additional, more accurate information about the equatorial ionosphere in its equilibrium and turbulent states.