Open AccessAnalysis of geomagnetic variations in south‐western Nigeria
Author(s) -
Ogunade S. O.
Publication year - 1995
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.1995.tb03518.x
Subject(s) - earth's magnetic field , geology , equatorial electrojet , daytime , equator , magnetic dip , magnetic declination , electrojet , climatology , geophysics , geodesy , oceanography , latitude , magnetic field , atmospheric sciences , physics , quantum mechanics
Geomagnetic variations, observed at 11 sites in south‐western Nigeria, have been analysed to derive interstation transfer functions with the site at Ile‐Ife as reference station. The study involves frequencies from 1 to 6 c.p.h. The reference station Ile‐Ife is 160 km northward of the continental slope off the Nigerian coastline and 400 km southward of the dip equator. The analysis has been carried out separately with selected data sections of a few hours length during daytime and during the night. Thus expressed linear relations between field components are in the case of day events of dual implication: (1) for the source field structure of the equatorial electrojet, (2) for internal conductivity conditions, including the coast effect from the Bight of Benin. Conductivity anomalies are the sole cause for an observed spatial variability of night events. A 2‐D thin‐sheet conductivity model has been derived taking both the source and the coast effect into consideration. This model provides a reasonably good fit between observed and computed transfer functions during day and night.