Abstract
<p>The influence of solar activity on magnetic measurements taken during the Italian repeat station surveys performed in 1999/2000 and 2009/2010 has been investigated. A method to estimate the difference between the 2000.0 and 2010.0 surveys in terms of the "residual" (i.e. not completely reduced) external contribution is proposed. This method is also based on the removal of the contribution due to the magnetic field of internal origin by means of CHAOS3 model from magnetic repeat station measurements. The origin of the observed differences is interpreted in terms of the very different level of solar activity between 2000.0 and 2010.0. Indeed, results seem to suggest that differences could be attributed to the enhanced ring current intensity during a phase of solar maximum. The investigation of the spatial patterns of these differences suggests that they could be reduced by introducing a larger number of variometer stations, especially during surveys performed under conditions of high solar activity.</p>
Highlights
As many other countries worldwide, Italy has a long standing tradition in magnetic repeat station surveys, and since 1979 measurements have been repeated regularly every five years at about a hundred points distributed quite uniformly on the Italian territory [Molina et al 1985, Meloni et al 1988, Meloni et al 1994, Coticchia et al 2001, Dominici et al 2007, Dominici et al 2012]
The purpose of this paper is to investigate if measurements of the Italian magnetic repeat station surveys can be affected by additional external fields due to enhanced solar activity
The paper is organized as follows: in Section 2 we briefly describe the data used and our method of analysis in Section 3 we illustrate the application of this method to the Italian magnetic network data together with a discussion of results
Summary
As many other countries worldwide, Italy has a long standing tradition in magnetic repeat station surveys, and since 1979 measurements have been repeated regularly every five years at about a hundred points distributed quite uniformly on the Italian territory [Molina et al 1985, Meloni et al 1988, Meloni et al 1994, Coticchia et al 2001, Dominici et al 2007, Dominici et al 2012] These measurements allow the compilation of magnetic charts that are generally used for navigational purposes, and representing and modeling the geomagnetic field and its secular variation on the regional scale [De Santis et al 2003] with a detail that would not be achievable only using data from the two Italian magnetic observatories of L'Aquila (AQU) and Castello Tesino (CTS). It is known that a magnetic measurement on the ground includes essentially two magnetic fields: one of internal origin and the other of external origin
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