Equatorial Counter Electrojet Longitudinal and Seasonal Variability in the American Sector Journal of Geophysical Research: Space Physics

The equatorial electrojet occasionally reverses during morning and afternoon hours, leading to periods of westward current in the ionospheric E region that are known as counter electrojet (CEJ) events. Wepresent the first analysis of CEJ climatology and CEJ dependence on solar flux and lunar phase for the Brazilian sector, based on an extensive ground-based data set for the years 2008 to 2017 from the geomagnetic observatory Tatuoca (1.2°S, 48.5°W), and we compare it to the results found for Huancayo(12.0°S, 75.3°W) observatory in the Peruvian sector. We found a predominance of morning CEJ events for both sectors. The afternoon CEJ occurrence rate in the Brazilian sector is twice as high as in the Peruvian sector. The afternoon CEJ occurrence rate strongly depends on season, with maximum rates occurring during thenorthern-hemisphere summer for the Brazilian sector and during the northern-hemisphere winter for the Peruvian sector. Signi ficant discrepancies between the two sectors are also found for morning CEJ