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Title: Diurnal and seasonal variation of GPS-TEC during a low solar activity period as observed at a low latitude station Agra
Authors: Chauhan, Vishal
Singh, O P
Singh, Birbal
Keywords: Ionospheric total electron content (TEC)
GPS-TEC variation
Solar activity
Global ionospheric maps (GIMs) of TEC
Issue Date: Feb-2011
Publisher: NISCAIR-CSIR, India
Abstract: Employing a dual frequency GPS receiver at a low latitude station Agra (geographic lat 27.120N, long 78.890E, dip 41.10), India (located just outside the equatorial anomaly crest), the measurement of ionospheric total electron content (TEC) has been carried out since 24 June 2006. Three years of data for a low solar activity period during 01 August 2006 - 31 July 2009 has been analysed. The temporal, seasonal and solar activity dependence of GPS-TEC data has been studied for the ionospheric region around Agra. The results show that the mean TEC varies from a minimum at 0500 hrs LT (LT=UT+5.5 hrs) to a peak value at about 1400 hrs LT and then decreases. The lowest values of TEC have been observed in winter whereas highest values have been observed in equinox and summer. The variation of the data has been compared with the variation of three solar indices, i.e. EUV flux, 10.7 cm solar radio flux (F10.7), and sunspot numbers (SSN) during the period of analysis. It is found that all the solar indices show high correlation with day maximum TEC (TECmax) in the summer than in equinox and low correlation is shown in winter season. It is also found that the data show high correlation with F10.7 in the two seasons of summer and equinox while the same is found with EUV flux in winter. The correlation of TECmax and SSN is found to be low as compared to those of F10.7 and EUV flux in all seasons. The GPS-TEC data obtained at Agra station for the year 2009 has also been compared with global ionospheric maps (GIMs) of TEC and a very good correlation is found between the two. Further, GIMs of TEC have been analysed for five different latitudes along the common meridian of 800E longitude. The present study has been carried out for three months of the year 2009 in each season. The role of equatorial ionization anomaly (EIA) crest is clearly visible on TEC data. These results are significant for Agra station which is a new location in the low latitude sector of Indian region.
Description: 26-36
ISSN: 0975-105X (Online); 0367-8393 (Print)
Appears in Collections:IJRSP Vol.40(1) [February 2011]

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