Speaker
Description
The equatorial ionosphere undergoes a profound electrodynamic reconfiguration during the sunset period. The rapid decay of E-region conductivity modifies the electrodynamic coupling and current closure between the E and F regions. In combination with the F-region dynamo driven by thermospheric winds, this process gives rise to the Pre-Reversal Enhancement of the zonal electric field (PRE). The resulting increase in the upward E × B plasma drift lifts the F region to higher altitudes, creating favorable conditions for the development of the generalized Rayleigh–Taylor instability and the subsequent generation of equatorial plasma irregularities. The occurrence and intensity of these processes are strongly modulated by atmospheric wave coupling, solar activity, and geomagnetic disturbances. This work discusses the physical mechanisms governing the sunset electrodynamics of the equatorial ionosphere, with emphasis on the electrodynamic coupling between the E and F regions and its role in controlling plasma transport and instability development. Observational examples from ionosonde measurements will be presented to illustrate how key ionospheric parameters, including hmF2, foF2, vertical plasma drift, and spread-F signatures, can be used to investigate the evolution of equatorial ionospheric electrodynamics and the onset of plasma irregularities.