Mid-Latitude Total Electron Content Enhancements in the American Sector

This publication presents total electron content (TEC) measurements across the American continent, revealing that during the June solstice, the most significant TEC values are frequently observed over Central America in the Northern Hemisphere (NH). These TEC enhancements are observed during the afternoon hours, last for a few hours, and are confined to regions of eastward magnetic declination. They occur at magnetic latitudes poleward of 20°. Similar TEC enhancements are observed during the December solstice over the southern coast of Brazil and northern Argentina, as well as poleward of 20°, but in the southern hemisphere (SH), at locations where the magnetic declination is westward. TEC latitudinal profiles along two field lines of non-zero magnetic declination, one intersecting Central America and then extending over the Pacific Ocean, and the other on the east side of South America, for 2012, provide insight into the day-to-day and seasonal variability of these mid-latitude TEC enhancements (MLTE). These TEC increases develop during solar minimum and maximum periods, and are not associated with any scintillation level. In the NH, the TEC enhancements end up near 70° W longitude, where the field lines are parallel to the geographic north-south meridian (declination = 0°). In the SH, the western boundary of the MLTE structure lies near 70° W, suggesting that the importance of the magnetic declination must be ≠ 0 for the MLTE to develop. In these regions of non-zero declination, the plasma motion along the field lines depends on the north-south wind but also on the east-west wind.