Spread-F equatorial fountain of plasma irregularities

Abstract

A belt of abnormally large uplifting of the whole F region occurs over a comparatively narrow latitude of a bout 6° from the dip equator on the nights with strong equatorial spread F. This is accompanied with post-sunset decrease of F layer critical frequency, <i>f</i>₀F2, at equatorial latitudes and increase of <i>f</i>₀F2 at tropical latitudes. The whole phenomenon of equatorial spread F belt within ±30° dip latitude is suggested to be due to the enhanced fountain of plasma irregularities in the post-sunset period over the equatorial latitudes associated with the continuation and/or intensification of the eastward electric field over the magnetic equator beyond the ionospheric sunset period.