Hysell, D. L.Chun, J.Chau Chong Shing, Jorge Luis2018-07-132018-07-132004-12Hysell, D. L., Chun, J., & Chau, J. L. (2004). Bottom-type scattering layers and equatorial spread F.==$Annales Geophysicae, 22$==(12), 4061-4069. https://doi.org/10.5194/angeo-22-4061-2004index-oti2018http://hdl.handle.net/20.500.12816/1827Jicamarca radar observations of bottom-type coherent scattering layers in the post-sunset bottomside F-region ionosphere are presented and analyzed. The morphology of the primary waves seen in radar images of the layers supports the hypothesis of Kudeki and Bhattacharyya (1999) that wind-driven gradient drift instabilities are operating. In one layer event when topside spread F did not occur, irregularities were distributed uniformly in space throughout the layers. In another event when topside spread F did eventually occur, the irregularities within the pre-existing bottom-type layers were horizontally clustered, with clusters separated by about 30 km. The same horizontal periodicity was evident in the radar plumes and large-scale irregularities that emerged later in the event. We surmise that horizontal periodicity in bottom-type layer irregularity distribution is indicative of large-scale horizontal waves in the bottomside F-region that may serve as seed waves for large-scale Rayleigh Taylor instabilities.application/pdfenginfo:eu-repo/semantics/openAccessIonosphereEquatorial ionosphereIonospheric irregulartiesPlasma waves and instabilitiesinfo:eu-repo/semantics/articlehttp://purl.org/pe-repo/ocde/ford#1.05.01Annales Geophysicaehttps://doi.org/10.5194/angeo-22-4061-2004