GPS observations of mid-latitude TEC depletions

Abstract

We have used measurements of TEC values gathered by several networks of GPS receivers, which operated in Central America and the Caribbean region between 2010 and 2013 to investigate the morphology of TEC depletions that develop at magnetic latitudes higher than 20°. We found that these TEC depletions occur mainly during magnetic active conditions, persist for very long periods and are seen even during afternoon hours especially when the level of magnetic activity is high (K p > 5o). The large spatial coverage provided by the GPS receivers in these regions (>150 receivers) allows us to identify their origin and in some cases track their paths. We also employ TEC values from South America to study possible links with the formation of TEC depletions at low latitudes and TEC measurements from North America to determine their latitudinal extensions. The mid-latitude depletions do not appear to be related to auroral plasma processes or to storm enhanced densities (SED). We are studying the possibility that their initiation process is associated with the disturbance dynamo or prompt penetrating electric fields that develop during storm conditions.