Case studies of enhanced E-layer formation at high-latitudes following sudden commencement absorption events

This presentation examines the formation of an enhanced E-layer that blankets the F-layer following sudden commencement absorption (SCA) events. Our case studies illustrate that storm sudden commencement (SSC) events cause impulsive precipitation of the otherwise trapped high energy electron population and that the precipitation of these high energy electrons may create considerable but short lived electron density enhancements (ionisation) at all ionospheric altitudes and particularly in the D and E layers (60-120 km altitude). The effect on HF communication links is demonstrated