Variations of foE and foEs During Low and High Solar Activity Over Equatorial Latitude Station, Thailand

This paper presents the variations of E-layer critical frequency (foE) and Sporadic E (foEs) layer during low (2010) and high (2014) solar activity over Chumphon (Latitude 10.72°N, Longitude 99.37°E and Magnetic Dip Latitude 3.0°N) station, Thailand. Both foE and foEs parameters are manually scaled from ionograms recorded by FM/CW ionosonde at King Mongkut's Institute of Technology Ladkrabang, Chumphon campus, Thailand. Chumphon is located at the magnetic equator. The observed data in the year of 2010 and 2014 are analyzed for low and high solar activity, respectively. For foE, the data during daytime (07:00-18:00 LT) are analyzed. For foEs, the daily hourly values and the seasonal (March equinox, June solstice, September equinox and December solstice) variations are analyzed. The results showed that the variation of foE during low and high solar activity were similarly, increasing during sunrise hours, reaching the highest values during noontime (11:00-13:00 LT) hours and decreasing after noontime until sunset hours. However, the foE values in 2014 were higher than those in 2010 because the sunspot number in 2014 was higher than that in 2010. For foEs, the results showed that the monthly hourly median was the maximum values in June solstice season for both years while was the minimum levels in December solstice season for 2010 and in March equinox season for 2014, respectively. This study will be helpful for communication designs and model predictions in the future.