Two geomagnetic regional models for Albania and south-east Italy from 1990 to 2010 with prediction to 2012 and comparison with IGRF-11

Abstract

Here we present a revised geomagnetic reference model for the region comprising Albanian territory, southeast part of Italian Peninsula and Ionian Sea from 1990 to 2010 with prediction to 2012. This study is based on the datasets of magnetic measurements taken during different campaigns in Albania and Italy in the time of concern, together with a total intensity data set from the Ørsted and CHAMP satellite missions. The model is designed to represent the Cartesian components, X , Y , Z and the total intensity F of the main geomagnetic field (and its secular variation SV) for the period of interest. To develop the model, we applied a Spherical Cap Harmonic Analysis (SCHA) of the geomagnetic potential over a 16 • cap with most of the observations concentrated in the central 4 • half-angle. The use of a larger cap than that containing the data was made to reduce the typical problems in SV modelling over small regions. Also a new technique, called "Radially Simplified Spherical Cap Harmonic Analysis" (RS-SCHA), was developed to improve the model especially in the radial variation of the geomagnetic field components. Both these models provide an optimal representation of the geomagnetic field in the considered region compared with the International Geomagnetic Reference Field model (IGRF-11) and can be used as reference models to reduce magnetic surveys undertaken in the area during the time of validity of the model, or to extrapolate the field till 2012.

Bulgarian Geomagnetic Reference Field (BulGRF) for 2015.0 and secular variation prediction model up to 2020

“…Models for some countries are developed by means of revised spherical cap harmonic analysis (R-SCHA) (Thébault et al, 2006;Korte and Thébault, 2007;Qamili et al, 2010). Others successfully use simpler procedures such as second-degree polynomial fitting (e.g IT-GRF: De Santis et al, 2003;Dominici et al, 2007;Ža-gar and Radovan, 2012) to represent the space and temporal behaviour of the field better than the global models.…”

Investigation of Regional Geomagnetic Field Modelling in Indonesia

“…Nevertheless, to compromise the boundary problem in the SCHA, the size of the cap can be enlarged in order to increase the spectral coverage in low harmonics, which is probably more significant (Torta et al, 1992). Then, the gaps in data distribution are filled with IGRF values as in Torta et al (1992) and Qamili et al (2010). Many regional reference fields have been calculated using SCHA methods, such as the model for Canada (Haines, 1985b), Scandinavia (Nevanlinna et al, 1988), Italy (De Santis et al, 1990), Spain (Torta et al, 1993), Albania and South-East Italy (Qamili et al, 2010), and several other models.…”

“…Scandinavia (Nevanlinna et al, 1988), Italy (De Santis et al, 1990), Spain (Torta et al, 1993), Antarctica (Torta et al, 2006), the Pacific Ocean (Toh et al, 2007), and Albania and South-East Italy (Qamili et al, 2010). Moreover, the SCHA technique has been developed into several modelling techniques, e.g., TOSCA (Translated Origin Spherical Cap Harmonic Analysis) by De Santis (1991), R-SCHA, the revised version of the SCHA, which is suitable to model the multilevel magnetic data (Thébault et al, 2006) and R-SCHA2D, an alternative version of the SCHA and R-SCHA which is suitable for modelling geomagnetic data at a quasi-constant altitude (Thébault, 2008).…”

“…Research by Qamili et al (2010) used a half-angle of 16°, although their data mostly concentrated in the central 4° half-angle. Torta et al (1992) and Torta and De Santis (1996) explain that the RMS residual of the SCHA model decreases as the cap halfangle increases.…”

“…The contour map of the difference between SCHA with index = 7 and the IGRF model is shown in Figure 30 Nonetheless, the IGRF itself is designed to exclude the contribution of the crustal magnetic field . Qamili et al (2010) explained that more detailed results were accomplished by regional modelling when they compared the IGRF and the SCHA model in Albania and Southeast Italy. However, extremely positive and negative areas arise around Vietnam.…”