A. B. Rabiu1 * , A. I. Mamukuyomi1 and E. O.
Joshua2
1Department of Physics, Federal University of Technology, Akure,
Nigeria
2 Department of Physics, University of Ibadan, Ibadan, Nigeria
Abstract. The variability of equatorial ionosphere has been examined by using ground based geomagnetic field data of horizontal and vertical field inten- sities obtained at the isolated terrestrial equatorial station of Ibadan (07.22o N 03.58o E). The values of Sq daily variation rises from the early morning period to maximum at about local noon and falls to lower values towards evening. The ionospheric current responsible for the magnetic field variations is inferred to build up at the early morning periods and attain maximum intensity at about local noon. The daytime variation in resultant solar quiet daily variations Sq in horizontal and vertical field intensities Sq(H) and Sq(Z) respectively were generally greater than night time. The rising rate of the ionospheric Sq cur- rent is generally greater than the decay rate. The vertical daytime ExB drift velocity in the ionospheric F region and the daytime strength of the equatorial electro jet are inferred to have seasonal variation. The scattering of variation is more on the disturbed condition than the quiet condition. This is obviously due to the ionospheric disturbances originating from external drives, such as, space weather effects, storms, etc. The seasonal variation is attributed to seasonal shift in the mean position of the Sq current system of the ionospheric electro ject and the electrodynamics effects of local winds. Magnitude of the annual means is greater in element H than Z at any given condition.
Keywords: equatorial ionosphere - currents - geomagnetic field