Spherical Elementary Current Systems Method Applied to Geomagnetic Field Modeling for the Adriatic

Eugen Vujić,Mario Brkić

doi:10.1515/acgeo-2016-0045

Abstract

The aim of this work was to derive an accurate regional model of geomagnetic components on the Adriatic. Data of north, east and vertical geomagnetic components at repeat stations and ground survey sites enclosing the Adriatic Sea were used to obtain a geomagnetic model at 2010.5 epoch. The core field was estimated by use of the global Enhanced Magnetic Model, while the crustal field by a mathematical technique for expanding vector systems on a sphere into basis functions, known as spherical elementary current systems method. The results of this method were presented and compared to the crustal field estimations by the Enhanced Magnetic Model. The maps of isolines of the regional model are also presented.

Highlights

Several methods for modeling of a spatial distribution of geomagnetic field components over a limited region at the Earth’s surface have been developed (Haines 1985, De Santis et al 1990, Thébault et al 2006). Haines (1985) introduced Spherical Cap Harmonic Analysis (SCHA), where the solution of Laplace’s equation over the spherical cap includes associated Legendre functions of non-integral degree and integral order
In this work the regional model is a combination of the Enhanced Magnetic Model (EMM) for the core field, and a model of the crustal field which was derived by the spherical elementary current systems (SECS) method, introduced by Amm (1997)
To find the optimal values of parameters of the SECS method, implemented for the crustal field modelling, the method was tested by using a known model of crustal magnetic field, as follows

Summary

Introduction

Several methods for modeling of a spatial distribution of geomagnetic field components over a limited region at the Earth’s surface have been developed (Haines 1985, De Santis et al 1990, Thébault et al 2006). Haines (1985) introduced Spherical Cap Harmonic Analysis (SCHA), where the solution of Laplace’s equation over the spherical cap includes associated Legendre functions of non-integral degree and integral order. In this work the regional model is a combination of the Enhanced Magnetic Model (EMM) for the core field, and a model of the crustal field which was derived by the spherical elementary current systems (SECS) method, introduced by Amm (1997). The SECS method is not based on spectral decomposition of a scalar magnetic potential (Amm and Viljanen 1999) It is based on two sets of basis functions (curl-free and divergencefree) in spherical coordinates, which can be used, e.g., to expand any continuously differentiable vector field on a sphere (Amm 1997, Amm and Viljanen 1999, Juusola et al 2006). The SECS method can expand the measured ground geomagnetic field into a sum of the magnetic field contributions of spherical elementary current systems, placed above the measurement sites and at some depth inside the Earth in geocentric frame (Pulkkinen et al 2003)

Objectives

Methods

Results

Conclusion