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.
