Abstract
<p>This paper presents the first results of vertical total electron content (VTEC) data from (1) a dual-frequency GPS receiver installed at the Chiang Mai University in Chiang Mai <em>(CHGM, 18.480 N, 98.570 E)</em> as part of SCINDA (Scintillation Network and Decision Aid) and (2) the International GNSS Service (IGS) station Pathum Wan (<em>CUSV, 13.735 N, 100.533 E</em>) with magnetic latitude of 8.69°N and 3.92°N respectively in Thailand, from August 2010 to July 2012. In the equatorial ionization anomaly (EIA) region, these two stations are separated at a distance of 668 km. Observed GPS-TEC values were found to be the highest between 1500 and 1900 Local Time (LT) throughout the study period at both the stations. The GPS-TEC data from both the stations was plotted diurnal, monthly and seasonal analyses were performed. The equinox (March, April, September, and October) and solstice (January, February, June, July, and December) periods had maximum and minimum diurnal peak variations, respectively, of the GPS-TEC. High TEC values are attributed to extreme solar ultra-violet ionization coupled with upward vertical E×B drift. A comparison of the GPS-TEC data from both the stations for the study period shows that the CHGM station recorded higher values of TEC than the CUSV station because of the formation of an ionization crest over the CHGM station. The GPS-TEC values also exhibited an increasing trend-because of the approach of solar cycle 24. For data validation, the diurnal, monthly, and seasonal variations in the measured TEC were compared with the TEC modelled in the International Reference Ionosphere (IRI) models (IRI-2007 and the recently released IRI-2012 model). The IRI-2007 shows good agreement with the data from 2010 to 2011 from both stations and IRI-2012 agrees well with the data from 2012 onwards compared to IRI-2007.</p>
Highlights
Global Navigation Satellite System (GNSS) has played a vital role in research involving atmospheric sensing worldwide
Chiang Mai station (CHGM): we have presented the seasonal variations of total electron content (TEC) from July 2010 to August 2012 observed at the Chiang Mai station (CHGM) and Pathum Wan (CUSV) and compared those values with IRImodels
Data at Chiang Mai and International GNSS Service (IGS) equatorial stations, in Thailand were compared with the International Reference Ionosphere (IRI)-2007 TEC and IRI2012 TEC from August 2010 to July 2012
Summary
Global Navigation Satellite System (GNSS) has played a vital role in research involving atmospheric sensing worldwide. In addition to IGS stations, many independent GNSS networks have evolved with time, leading to the availability of large datasets across the globe. One such network, Scintillation Network and Decision Aid (SCINDA) was established by the Air Force Research laboratory of USA, as a set-up of ground based stations that monitor trans-ionospheric signals at the VHF and L Band frequencies. The SCINDA ground stations are generally positioned between the equatorial ionization anomaly (EIA) region, as these locations experience the strongest global levels of scintillation [Carrano and Groves 2006]. The equatorial anomaly forms when vertical drift velocities push the F-region plasma to the higher heights over the equatorial region. Adding to an ample scope of studying EIA patterns during diurnal, seasonal, annual, solar cycle dependent period in a wide range of time scales
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
