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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 35, issue 5
Ann. Geophys., 35, 1085–1092, 2017
https://doi.org/10.5194/angeo-35-1085-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: The Earth’s magnetic field: measurements, data, and applications...

Ann. Geophys., 35, 1085–1092, 2017
https://doi.org/10.5194/angeo-35-1085-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Regular paper 12 Sep 2017

Regular paper | 12 Sep 2017

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

Metodi Metodiev and Petya Trifonova Metodi Metodiev and Petya Trifonova
  • Department of Geophysics, National Institute of Geophysics, Geodesy and Geography-BAS, Sofia 1113, Acad.G. Bonchev str., Bl. 3, Bulgaria

Abstract. The Bulgarian Geomagnetic Reference Field (BulGRF) for 2015.0 epoch and its secular variation model prediction up to 2020.0 is produced and presented in this paper. The main field model is based on the well-known polynomial approximation in latitude and longitude of the geomagnetic field elements. The challenge in our modelling strategy was to update the absolute field geomagnetic data from 1980.0 up to 2015.0 using secular measurements unevenly distributed in time and space. As a result, our model gives a set of six coefficients for the horizontal H, vertical Z, total field F, and declination D elements of the geomagnetic field. The extrapolation of BulGRF to 2020 is based on an autoregressive forecasting of the Panagyurishte observatory annual means. Comparison of the field values predicted by the model with Panagyurishte (PAG) observatory annual mean data and two vector field measurements performed in 2015 shows a close match with IGRF-12 values and some difference with the real (measured) values, which is probably due to the influence of crustal sources. BulGRF proves to be a reliable alternative to the global geomagnetic field models which together with its simplicity makes it a useful tool for reducing magnetic surveys to a common epoch carried out over the Bulgarian territory up to 2020.

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For regional studies and practical use regional-scale models of the geomagnetic field are necessary. The Bulgarian Geomagnetic Reference Field (BulGRF) for 2015.0 epoch and prediction up to 2020.0 is produced and presented in this paper. It uses data from Panagyurishte (PAG) observatory and the Bulgarian secular network. As a result, our model gives a set of six coefficients which allow the users to obtain the main field values using only the geographic coordinates and a simple calculator.
For regional studies and practical use regional-scale models of the geomagnetic field are...
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