CONTRIBUTIONS OF DIFFERENT HARMONICS OF SELECTED IONOSPHERIC AND GEOMAGNETIC PARAMETERS TO THEIR VARIATIONS

Abstract

Solar quiet daily variations (Sq) in three geomagnetic elements namely the horizontal intensity (H), declination (D) and vertical intensity (Z) are investigated for the influence of their smaller waves (local effects) on the observed variations (global effect). The Sq variations at two stations within the equatorial region, namely Ilorin (ILR) in West Africa (8o 29' N, 4o 32' E) and Addis Ababa (AAB) in East Africa (9⁰ 01' N, 38⁰ 44' E) comprising of geomagnetic field components H, Z and D acquired with the MAGDAS facility at the observatories in collaboration with ICSWSE (Japan) were subjected to twenty four point numerical harmonic analysis and decomposed to extract the required harmonic amplitudes and Fourier phasing. Results show a general diurnal predominance, with semi diurnal, ter diurnal and quarter diurnal components switching dominance intermittently across seasons. A normalized percentage harmonic equation is defined for the first time to give numerical assessments of the contributions of local effects to the global effect. Our result shows that diurnal contribution controls the magnitude and pattern of variations of the parameters analyzed. The investigation serves to present a means to determine pattern of variations of physical data with respect to timescale. The phase angles indicate the relative timing of the influence of local effects on the global effects. Akure (7 o 15'N, 5 o 11'E) South West Nigeria TEC data (acquired by the SCINDA-Scintillation Decision Aid- facility at FUTA) for selected equinox and solstice of the year 2009 were also treated for the same investigation to demonstrate the suitability of our methodology for physical data when it is desirable to get more from a given dataset. The contribution of the local TEC variations to the global TEC variations of Akure has been estimated. Results of the Fourier based eigen analysis of TEC data show strong diurnal variations for the months of investigated. Results of this research may be used to improve or reconstruct ionospheric and geomagnetic models.