Plasma density discontinuity and spread F

Abstract

It is shown that the generation of the equatorial spread F irregularity in the post-sunset period need not he always at the base of the F region. The irregularities are generated at the E region, provided there existed a retardation type E2 layer or a uniform blanketing sporadic E layer before the sunset. The irregularities are generated even at the region close to the altitude of peak ionization density, provided there is a discontinuity in the plasma density variation with height (a kink or a G layer). It is suggested that if proper electric fields are present at the sunset period, then the spread F irregularities are generated at any altitude having plasma density discontinuity.