Comparison between the foF1 and foF2 critical freqeuncy in equatorial region of Malaysia

The ionosphere is the topside of the atmosphere that contains high concentration of ions and can reflect radio waves due to refraction. The ionospheric region of interest is located above the equatorial region at longitude 1° 52´ and latitude 103° 48´ (Parit Raja, Johor). The observations of the ionospheric critical frequency were made from 2005 to 2007. The critical frequency is determined by using the monthly median value for each day. Regression analysis was used on the theoretical and observed value. The observed value is obtained from ionogram measurements with five-minute intervals using logarithmic frequency steps from 1 Mhz to 20 Mhz. The sunspot number is used as a parameter to compare the values of critical frequency at high sunspot and low sunspot numbers for the day. The foF2 critical frequency for 2005, 2006 and 2007 show that the higher value is for 2005, 11 MHz while the critical frequency is much lower for 2006 and 2007, 9.7 MHz and 8.95 MHz. The correlation analysis was used to determine the relationship for the yearly value. The correlation was made using the median value of the foF2 critical frequency from 2005 until 2007. The regression and correlation analysis of the critical frequency was able to show the trend of the critical frequency for 2005, R² = 0.031, 2006, R² = 0.112 and 2007, R² = 0.017.