Dynamics of the Arecibo ionosphere: A case study approach

A number of different processes have been suggested to explain the F layer plasma drifts measured over the Arecibo Observatory. A series of experiments are described here which take advantage of neutral wind measurements now available at Arecibo as well as an unusual event during which large high‐latitude electric fields penetrated to the low‐latitude ionosphere. With this added information we are able to differentiate between the competing processes controlling the F layer. We show that depending on various conditions, both the F layer dynamo mechanism and the external electric field‐diffusion velocity mechanism can control the dynamics of the F layer. We also present a case in which neither of these mechanisms is sufficient to explain the observed behavior of the nighttime F layer plasma. In addition, we have carried out calculations that demonstrate that during magnetically active times, the penetration electric fields can set the low‐latitude thermosphere in motion via ion drag. Finally we show that at times, conjugate point electric fields appear to be present and that the conductivity at the conjugate point can dominate the local value with observable consequences.