Seasonal characteristics of COSMIC measurements over Indian sub-continent during different phases of solar activity

The seasonal characteristics of F2 region is investigated using peak electron density (NmF2) and corresponding altitude (hmF2) measurements obtained by COSMIC observations over Indian sub-continent (Geog. 5-40°N and 60-100°E) for the complete mission during the solar cycle 24 (Apr, 2006-Dec, 2013). A stronger EIA is observed in summer and winter during high solar activity whereas occurs in equinoxes during all levels of solar activity. The noontime winter anomaly in NmF2 is absent/weaker during low (2006-2009)/high (2010-2013) solar activity over equator whereas is stronger in low and moderate solar activity (2006-2007 and 2010-2011) but absent in minimum and maximum (2008-2009 and 2012-2013) solar activity over low-latitude respectively. The higher hmF2 is observed over the equator throughout the day (equator: 230-415 km and low-latitude: 220-340 km). The observed parameters, NmF2 and hmF2 are compared with the IRI-modeled values using CCIR and URSI options. The comparison exhibits a higher discrepancy in NmF2 in nighttime and morning for equatorial and lower discrepancy for the whole day over the low-latitude whereas smaller (<20%) discrepancy exists in the hmF2 throughout the day using both IRI options. In conclusion, we found CCIR option in more agreement to the observed values for both equatorial and low-latitude regions respectively.