The F2-region equatorial anomaly in the African, American and East Asian sectors during sunspot maximum

Appleton anomaly increase following sunset: Its observed relation to equatorial F layer E × B drift velocity

“…However, the levels near the equator during these times are found to be similar from day to day in their magnitudes and in the fact that they decrease with time [Whalen, 1993]. In addition, these levels are also consistent with those found by Wright [1962] and Lyon and Thomas [1963] on quiet days at these local times during the equinoxes of 1958. Thus, while the detailed structure near the equator is not resolved during this period, the definition of the crest is not significantly affected.…”

The equatorial F-layer: progress and puzzles

“…Among many studies using ionosonde data, Lyon and Thomas (1963) and Thomas (1968) analyzed quiet-day data from three ionosonde chains. They found that the latitude variation is asymmetrical at solstice, with NmF2 greater on the summer side of the magnetic equator at night and greater on the winter side by day.…”

“…It is ®tting for it to be represented in this volume that celebrates the scienti®c career of Lance Thomas, whose contributions to ionospheric science include studies of the equatorial region (Lyon and Thomas, 1963;Thomas, 1968).…”

IRI-2001 model predictions compared with ionospheric data observed at Brazilian low latitude stations

“…Earlier papers by Lyon et al (1963) and Shastri et al (1996) suggest that there is a differential shift of the EIA crests with solar activity for different seasons in different longitude sectors. Shastri et al (1996) have presented comparison between the observed data and predictions of the IRI-90 in the Indian sector.…”