Characterization of low latitude GPS-TEC during very low solar activity phase

Study of Ionospheric TEC from GPS observations and comparisons with IRI and SPIM model predictions in the low latitude anomaly Indian subcontinental region

“…Also the meridional neutral wind component blowing from summer to winter obstructs the anomaly crest development in the Summer hemisphere and enhances in the Winter hemisphere (Bramley and Young, 1968;Torr and Torr, 1973;Rishbeth et al, 1995;Tsai et al, 2001). The increased value of December solstice than June solstice has been explained earlier by Zhao et al studies of Chauhan and Singh (2010), Galav et al (2010) and Bagiya et al (2011) report reversely during low solar activity period which is concurrent with results at Lucknow station only. However, the high solar activity towards the end of year-2011 enhanced the overall TEC at the northern anomaly region.…”

Patterns of GPS-TEC variation over low-latitude regions (African sector) during the deep solar minimum (2008 to 2009) and solar maximum (2012 to 2013) phases

“…According to their findings, both crests move significantly equatorward in winter than other seasons, and there is a tendency for both crests to appear earlier in winter and later in summer. Galav et al (2010) also depicted as the seasonal variations in daytime TEC show a semiannual periodicity, with a minimum in winter over the Indian regions. In addition, over a low-latitude Singapore station, Kumar et al (2014) have noted that the GPS-TEC values get decreased between 0300 and 0430 UT and started to increase between 0430 and 0930 UT during the period of 2011.…”

“…In addition, the peak hourto-hour VTEC values observed in the high solar activity phase are larger than the corresponding peak values observed in the low solar activity phase, by more than two times (see Figure 2) Furthermore, small enhancements in the VTEC values are observed in the nighttime variation of VTEC nearly between 1800 and 2000 UT (2100 and 2300 LT), especially for days considered from equinoctial months and then drops again (mostly after 2300 UT). According to Galav et al (2010), this may be due to the pre-reversal enhancement which is attributed to variation of the vertical F region drifts which are large and upward during 18 to 20 LT over the equator. The F region plasma is raised further up under the influence of the enhanced vertical drift at the equator during the equinoxes.…”

Statistical analysis of TEC perturbations over a low latitude region during 2009–2013 ascending solar activity phase

“…Solar activity variations affect the E region electric fields, thus influencing the strength of the EIA as well as the magnitude of EEJ. Galav et al (2010) observed a contraction in the crest of the EIA during a declining solar activity period. Magnetospheric electric fields during storms may also suppress or enhance the fountain effect at the geomagnetic equator.…”