The Italian magnetic repeat station network: results from the 2012.5 ‘Reduced Network’ completion

Abstract

In Italy INGV (Istituto Nazionale di Geofisica e Vulcanologia) has systematically undertaken the task of periodic making measurements of the Earth's magnetic field on a network of more than 110 points (repeat stations), with an average spacing around 55-60 km. Measurements are repeated regularly every 5 years and the last published data reports and magnetic maps, refer to 2010.0, available in Dominici et al, 2012. At that time the report referred to a survey of 131 repeat stations (including 2 observatories, 11 stations in Albania, 3 stations in Corsica and 1 in Malta) carried out between 2009 and 2010, also with the purpose of updating the national magnetic cartography. At the epoch 2012.5 a selection of stations, from the first order Italian Magnetic Network, selected on the basis of the lowest amplitude values of anomaly with respect to a 'normal' field, was repeated. The number of the selected stations amounts to 25, distributed according to an almost uniform national geographical coverage, with an average spacing around 100 km. Secular variation and analytical expressions, such as second order polynomials, in latitude and longitude for all field elements, were determined and coefficients were obtained for the spatial field variation and secular variation. We describe here the characteristics of this reduced network with the data reduction procedure, normal fields and maps, and compare the results with other magnetic field models.