News // Paper - The Tropical Anomaly

The Tropical Anomaly

Cesar E. Valladares, Vince Eccles

Corresponding Author information:

Cesar E. Valladares
Institute for Scientific Research, Boston College
Room 217, Kenny Cottle Hall
885 Centre Street, Newton, MA 02459
Phone: +1-617-552-8789
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Key points:

Largest TEC over Central America during June solstices
Demonstrated the anomalous TEC is due to zonal wind and magnetic declination
The anomaly is symmetric occurring in South America during December solstice.


Continuous and regional measurements of total electron content (TEC) over the Americas have revealed that quite frequently the largest TEC values reside over Central America. These unexpected and anomalous TEC values have not been reported before. They are observed during the June solstice afternoon hours, last for a few hours, are constrained to regions of eastward magnetic declination and occur at magnetic latitudes poleward of 20°. During the December solstice, similar TEC enhancements are seen over the southern coast of Brazil, also poleward of 20°, but in a region where the declination is westward. It is proposed and demonstrated using a physics-based model of the low-latitude ionosphere, that the TEC enhancements are produced by the neutral winds blowing at longitudes where the Earth’s magnetic declination is different from zero. Due to their anomalous character, the TEC enhancements have been designated as the tropical anomaly.

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