On Data Interpolation at Three Croatian Repeat Stations by Using the Spherical Elementary Currents Systems Method

Eugen Vujić

doi:10.1515/acgeo-2016-0005

Abstract

A general mathematical tool for expanding vector systems on a sphere into basis functions, spherical elementary current system (SECS) method, was applied for separation of the geomagnetic field variations into external and internal parts, over a limited region of central and southeastern Europe. The registered variations at three Croatian repeat stations were compared to the variations estimated by the SECS method using the variations from the different sets of observatories. The results of the SECS method were also compared to a simple assumption that the variations at repeat station are equal to those at particular observatory. The relevance of this comparison was to get an insight about the possibility of using the SECS method for estimating the geomagnetic field variations over Croatia. The guidelines for the application of the SECS method for the purpose of reducing repeat station data were also given.

Highlights

The geomagnetic field measured at the Earth’s surface is a superposition of several contributions
The method of spherical elementary current systems was implemented for interpolation of geomagnetic time variations at three Croatian repeat stations for the first time
The data from different sets of geomagnetic observatories were used for interpolation of geomagnetic time variations at the positions of repeat stations

Summary

Introduction

The geomagnetic field measured at the Earth’s surface is a superposition of several contributions. The external field variations (and associated induced effects) at some repeat stations and at surrounding observatories can be prominently different, and this occurs, e.g., when these sites are quite far away (especially in latitude), and/or the lithospheric electrical conductivity differs under these sites (Korte and Thébault 2007). The time variations at some point can be interpolated by using the data recorded at relatively nearby magnetometers, up to few hundreds of kilometers, by using the simple assumption that these variations (about some arbitrary baselines) are the same at those sites. Such a method is commonly used in repeat stations data reduction procedure (Newitt et al 1996)

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