Relationship between long trem changing of foF2 frequency and earth?s magnetic field

Earth?s ionosphere is a important factor in space weather investigations and the variability of the ionosphere is important for the ionopsheric physics and radio communications. In today? s technology one of the most important characteristic property of the communication systems is the making life easier by helping people to get the latest information in a sense of quality and speed. The characterizing propert of the ionosphere is the electron density distribution that shows varition as a function of height, latitude, longtitude, local time, geomagnetic activity and solar activity. Especially, the magnetic activities at Sun have huge effects on the ionospheric dynamics. This results in the influence of the Earth?s magnetic field by changing the ionospheric critical frequency.In this study, relationship between ionospheric critical frequency variation of F2 layer and Earth?s magnetic field has been investigated. Ionospheric foF2 datas were obtained from ionsonda station in Manila (121.1o E, 14.7o N). The Dst index were obtained from World Data Center. In order to investigate the effect on the foF2 of solar activity has been used foF2 datas of the high solar activity year (1981) and low solar activity year (1985). In order to investigate the effect of season, in each year all days were divided into three seasons, namely, equinox (March, April, September and October), summer (May, Jane, July and August) and winter (November, December, January and February). In order to investigate how foF2 varies and the extent of variation, linear regression analysis was used for each local time. Besides lagged regression analysis was used to investigate the lagged effect of magnetic field. Response of foF2 to Dst shows obvious especially in the high solar activity period. Generally, Earth?s magnetic field cause foF2 to increase at daytime and decrease at nighttime. Seasonal dependence of the diurnal variations of foF2 is very obvious.The solar cycle has important effect on the diurnal variations of foF2.Key Words: foF2, Earth?s Magnetic Field, Time-Lagged Regression Analysis