Mapping of electric field structures from the equatorial F region to the underlying E region

The theories of electrostatic fields in the equatorial ionosphere attributed to Farley [1960] and Spreiter and Briggs [1961] are reviewed, and a hybrid of these theories is applied to investigate how spread F irregularities map down to the underlying E region. It is found that structures larger than 1 km map easily through the E region, while smaller structures do not. This implies that in general, subkilometer F region irregularities cannot directly generate image striations in the underlying E region, a result which affects previous investigations of the role of images in equatorial spread F.