ITalian Geomagnetic Reference Field (ITGRF): update for 2000 and secular variation model up to 2005 by autoregressive forecasting

A. De Santis, L. Gaya-Piqué, G. Dominici, A. Meloni, J. M. Torta, R. Tozzi


The updated version of the ITalian Geomagnetic Reference Field (ITGRF) for 2000.0 and its secular variation model
up to 2005.0 are presented in this paper. The main field model is based on a simple polynomial approximation in
latitude and longitude of the geomagnetic field elements computed from IGRF on a 12° ¥ 11° grid centred over
Italy. The annual means from L'Aquila observatory were used to determine the baseline level, imposing a constant
observatory anomaly bias. This procedure gives a set of 6 coefficients every 5 years from 1960 to 2005 for the
horizontal H, total field F, vertical Z and declination D elements of the geomagnetic field. The extrapolation of
ITGRF to 2005 is based on an autoregressive forecasting of the L'Aquila observatory annual means. Comparison
of the field values computed from the model with those recorded at the other Italian observatory (Castello Tesino)
shows that the ITGRF improves the fit of the secular variation pattern with respect to the global IGRF model by
a factor of 3. The ITGRF represents a reliable alternative to global models when reducing magnetic surveys to a
common reference epoch over the Italian region.


geomagnetic reference field;secular variation;autoregressive forecasting

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Published by INGV, Istituto Nazionale di Geofisica e Vulcanologia - ISSN: 2037-416X