Spherical harmonic representation of the geomagnetic fields in the Nigeria sector of the Niger delta basin

Abstract

A 0.5 x 0.5 representation of the geomagnetic elements and their rates of change have been predicted for the Nigeria sector of the Niger Delta basin using the spherical harmonic analysis. The geomagnetic elements computed are the total field (F), horizontal field (H), north component (X), east component (Y), vertical component (Z), declination (D), inclination (I) and their rates of change, D Z Y X H F ∆ ∆ ∆ ∆ ∆ ∆ , , , , , and I ∆ respectively. The geomagnetic elements were predicted using the latest IGRF-10 (10th Generation International Geomagnetic Reference Field) model which allows prediction of spot values of magnetic field. The spherical harmonic representation of the geomagnetic fields enables the regional field which has its origin from the outer core of the earth to be estimated. This approach of computing the regional fields is globally accepted and eliminates the problems that may arise when adjacent magnetic surveys are combined. It solves an additional problem of extreme interpolation of magnetic values due to lack of magnetic observatory in the Niger Delta. The highest total intensity for the region is 33431.0nT and the secular variation of the total field intensity is marked by decrease of 25.8nT/yr to 20.0nT/yr. The variations in geomagnetic values and the values computed for 2010.0 epochs reflect the current behavior of the geomagnetic field and the geodynamics of the earth’s interior under the region.