Characterization of equatorial plasma depletions detected from derived GPS data in South America

The equatorial plasma bubbles (EPBs) have been studied using slant total electron content (sTEC) derived from GPS data. The sTEC has been calculated from data measured at 15 International GNSS Service (IGS) stations located from 90°W to 30°W, covering the ionospheric equatorial anomaly at the American sector, for the years 2000, 2001, 2004, 2005 and 2008. The Ionospheric Bubbles Seeker (IBS) application has been used to detect and characterize the sTEC depletions associated to the EPBs. This technique bases its analysis on the time-variation of the sTEC and the population variance of this time-variation. The default configuration has been used and an EPB has been considered when a sTEC depletion was greater than 5 TEC units (TECu). The hourly occurrence shows the well-known maximum number of depletions after the post-sunset. The monthly occurrence of the EPBs is also analyzed and compared with previous studies. The International Reference Ionosphere model (IRI) has been used to calculate the equatorial vertical drift (EVD) and the peak densities of the E- and F-layers (NmE and NmF2, respectively). The EVD variation has been compared with the seasonal variation of the EPB. A discussion between the yearly mean occurrence EPBs rate and the solar activity is included. The variation of the yearly mean depth and duration of the sTEC depletions with the solar activity conditions and its relation with the ionospheric characteristics given by the IRI model has been also studied.

► We used the IBS to study the EPBs at 16 IGS stations located in South America. ► We obtained greatest values of occurrence EPBs rate close to the magnetic equator. ► Seasonal variation has a strong correlation with the equatorial vertical drift. ► Characteristics of the EPB are related with peak densities of the E- and F-layers.