Abstract
The climatology of equatorial plasma bubbles (EPBs) for the period 1998–2008 was studied using slant total electron content (sTEC) derived from global positioning system (GPS) data. The sTEC values were calculated from data measured at 67 International GNSS Service (IGS) stations distributed worldwide around the geomagnetic equator and embracing the region of the ionospheric equatorial anomaly (IEA). EPBs and their characteristics were obtained using the Ionospheric Bubble Seeker (IBS) application, which detects and distinguishes sTEC depletions associated with EPBs. This technique bases its analysis on the time variation of the sTEC and on the population variance of this time variation. IBS finds an EPB by default when an sTEC depletion is greater than 5 TEC units (TECu). The analysis of the spatial behavior shows that the largest rate of EPB takes place at the equator and in the South America-Africa sector, while their occurrence decreases as the distance from the magnetic equator increases. The depth and duration of the sTEC depletions also maximize at the equator and in the South America-Africa sector and weaken departing from the equator. The results of the temporal analysis for the data of the IGS stations located in AREQ, NKLG, IISC, and GUAM indicate that the greatest rate of EPB occurrence is observed for high solar activity.
Highlights
Ionospheric irregularities are defined as ionospheric regions with electron density clearly different from the background volume
This paper aims to present the climatology of equatorial plasma bubbles (EPBs) for the period 1998–2008 at the global scale using worldwide data recorded at 67 International GNSS Service (IGS) stations located around the geomagnetic equator
global positioning system (GPS) observables obtained from Receiver INdependent EXchange (RINEX) files using the technique developed by Brunini & Azpilicueta (2009)
Summary
Ionospheric irregularities are defined as ionospheric regions with electron density clearly different from the background volume. They are the plasma expression of complex physical processes that can produce scintillation of the electromagnetic signals crossing the ionosphere and spread F in the equatorial ionograms. Density variations are defined as positive or negative if the anomaly with respect to the background shows an increase or a decrease in the number of electrons, respectively. Known as ‘‘blobs’’, were first reported by Oya et al (1986) and Watanabe & Oya (1986). The formation of the bubbles is very rapid due to very different and complex physical phenomena. The bubbles can adopt variable shapes and their size ranges up to seven orders of magnitude, from centimeters to hundreds of kilometers
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