F-region electril fields: Observational aspects

Abstract

Equatorial electric field measurements were recently reviewed by B. Balsley on occasion of the last equatorial symposium. We present in this review new measurements reported in the literature since the last symposium and include a large amount of new unpublished measure­ments of the vertical and East-West electric fields performed at Jicamarca using the incoherent scatter technique. The data base at Jicamarca comprises now almost a full solar cycle. The effects of low solar activity are discussed. The main effects being: (1) A reduction in the night-time maximum amplitude of the E-W drift; (2) an increase in the frequency of occurrence of afternoon reversals of the vertical drift (E-W electric field); (3) a reduction in the amplitude and fre­quency of occurrence in the prereversal (post-sunset) vertical drift enhancement.