Diurnal and seasonal variation of topside ionospheric ion density over Indian region at solar minimum and solar maximum

In the present paper in situ measurement of ion and electron parameters of ionosphere F2 region made by separate Retarding Potential Analyzers (RPAs) payload onboard the Indian satellite SROSS-C2 over Indian region (65–95°E and 5–35°N) for more than half of 23rd solar cycle are examined to analyse the ion density (nini) at an average altitude of ∼∼500 km (altitude range 500 ±± 100 km). The data-set is analysed for the diurnal and seasonal behaviour of nini and its dependence on solar activity by comparing the results for solar minima (1995, F10.7′95=77) and solar maxima (2000, F10.7′00=178) years. nini is found to exhibit the expected diurnal behaviour with day minimum in presunrise hrs. and maximum at local noon or afternoon. This trend is not affected by seasons or solar activity. However for different seasons, nini enhances with solar activity and more interestingly, nighttime values of nini are found to be affected by greater magnitude as compared to daytime corresponding values.