The polar-cap scintillation zone

Scintillation and other measurements from the HILAT program were used to study the zone at the edge of the polar cap where the most intense average scintillations are found. The maximum of the zone was found to be horseshoe shaped and located on the dayside. This scintillation zone shows only small variations with season and magnetic activity. On individual HILAT passes discrete onsets of intense scintillations are observed. Averaging to these onsets gives the high average scintillation intensities. The onsets appear to occur where irregularities are being created. These same locations show an increase in ionospheric electron content and an increase in the low energy electron flux. After creation the irregularities are convected towards the polar cap. The irregularity source region is also the region known as the 'dayside high-latitude auroral region' where the precipitating soft electron flux produces 630 nm auroras. (author)