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Satellite‐Based Augmentation Systems (SBASes) are designed to provide additional accuracy and robustness to existing satellite‐based radio navigation systems for all phases of a flight. However, similar to navigation systems such as GPS which has proven its worth for the investigation of the ionosphere, the SBASes do have certain advantages. In the present paper, we propose and demonstrate SBAS applicability to ionospheric and space weather research in a novel and cost‐effective way. The recent commissioning of the Indian SBAS, named GPS Aided Geo Augmented Navigation (GAGAN), covering the equatorial and low‐latitude regions centered around the Indian longitudes provides the motivation for this approach. Two case studies involving different ionospheric behavior over low‐latitude regions vindicate the potential of SBAS over extended areas.

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[1] The global wave number 4 structure in the Indian longitudinal region spanning from 70 to 95°E forming the upward slope of the peak in the total electron content (TEC) are reported along the crest of equatorial ionization anomaly (EIA). The continuous and simultaneous measurements from five GPS stations of GPS Aided Geo Augmented Navigation (GAGAN) network are used in this study. The long-term database (2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012) is utilized for examining the local time, seasonal, and solar cycle dependency on the longitudinal variations of TEC. Our results confirm the existence of longitudinal variations of TEC in accordance with wave number 4 longitudinal structure including its strength. The results suggest that these variations, in general, start to develop at~09 LT, achieve maximum strength at 12-15 LT, and decay thereafter, the decay rate depending on the season. They are more pronounced in equinoctial season followed by summer and winter. The longitudinal variations persist beyond midnight in equinox seasons, whereas in winter, they are conspicuously absent. Interestingly, they also exhibit significant solar cycle dependence in the solstices, whereas in the equinoxes, they are independent of solar activity. The comparison of crest-to-trough ratio (CTR) in the eastern (92°E) and western (72°E) extreme longitudes reveals higher CTR on the eastern side than over the western extreme, suggesting the role of nonmigrating tides in modulating the ExB vertical drift and the consequential EIA crest formation.Citation: Sunda, S., and B. M. Vyas (2013), Local time, seasonal, and solar cycle dependency of longitudinal variations of TEC along the crest of EIA over India,

The paper describes day to day changes observed in atmospheric aerosol's parameters namely AI 300, AOD 550 , , TWC,  and MC from their background reference day value over Udaipur during Pre to Post-Diwali period from 2002 to 2007. Before Diwali to Diwali, daily variations in such aerosol's parameters values show the substantial increase order of 30-60% from their respective background. Afterward Diwali, such change in AI 300 shows the decreasing behavior, in sharp contrast to this, daily variations in AOD 550 ,  and MC exhibit either lower value or attain the same peak value depending upon the corresponding level of TWC and rainfall activity of that particular year. These variations are not instantly but with certain delay in the same period. A considerable amount of implication in aerosols loading is observed in terms of reduction in SHWRF from 20-30% during the enhancement period of aerosol's parameters. However, DSWRF does not show any appreciable change. The main possible causes of increase in aerosol's loadings within above period are discussed in views of inter mixed effect of local emission activity and long range transport of aerosols from heavy polluted IGP site and in reduction of PBL height and wind speed.