DEPENDENCE OF VARIABILITY OF GEOMAGNETIC HORIZONTAL FIELD ON EQUATORIAL RING CURRENT.

Abstract

The study of the dependence of variability of geomagnetic horizontal field on equatorial ring current has been carried out using 14 African observatories. This study examined the diurnal, monthly and seasonal variations of H field using MAGDAS data set along African meridians with the geographic latitude between -400 to 300, hourly values of the H variation in the horizontal component of the earth magnetic field of the year 2009 in which the solar activity was empirically low (average sunspot number Rz = 3.1) were used. It can be seen that the midday H as well as the midnight H values of all stations are highly correlated with the corresponding Dst index, indicating that the day-to-day fluctuations in daytime H as well as nighttime H are largely due to the corresponding fluctuations in the strength of equatorial ring current, represented by Dst index. The daily fluctuations of H field exhibit a rise mostly during pre-noon hours and a decline during post-noon hours. The monthly variation showed that the station at the northern hemisphere shows variations that are larger than the southern hemisphere station through the variations in all the months of the year. The daily range of H do not seem to correlate with corresponding variations of Dst index as the midday H or midnight H field do.