On large-scale wave structure and equatorial spread F without a post-sunset rise of the F layer



[1] Large-scale wave structure (LSWS) and the plasma structure, referred to as equatorial spread F (ESF), are shown, for the first time, to develop on a night, when the post-sunset rise (PSSR) of the F layer was absent. Using ionograms from two nearby locations, together with measurements of total electron content, LSWS and ESF are also shown to coexist in regions that are bounded geographically. These results point to the undeniable importance of LSWS (as well as the PSSR) in the day-to-day variability in occurrence of ESF, and a need to use of a two-dimensional description of the electrodynamics.