Verification of 2020 Geomagnetic Models Over the Bulgarian Territory

AbstractHigh precision geomagnetic field measurements are performed in ground observatories, repeat stations and from the last 30 years - low Earth orbiting satellites. They bring considerable information about the nature and spatiotemporal behavior of the Earth’s magnetic field and its sources. Modelling procedures are necessary to unravel the information and to identify signals from each sources, as well as to predict the changes coming in the near future.Geomagnetic measurements from repeat station networks traditionally complement observatory data to provide better data coverage in larger areas and for detailed regional mapping. Bulgaria does have a tradition in the regular repeat station measurements despite some periods without campaigns due to lack of funding. As early as 1934, a secular network was established, which was later grown and is still used today. That gives us the opportunity to investigate the secular variation of the geomagnetic field over the Bulgarian territory and to analyze the accuracy of different regional and global scale models.In 2018, the Military geographical service of the Ministry of Defense with the support of the Geomagnetic observatory Panagjurishte started a new general geomagnetic field survey of Bulgaria. The plan is to re-measure all 473 evenly distributed and well-selected stations from the previous campaign accomplished 1978–1980. The territory is divided into four units (blocks) which were surveyed in four consecutive years. So far, two of the units have fully processed measurements and data reduced to the epoch 2020.0. The obtained results are compared with the global IGRF13 model to analyze its accuracy for regional field survey application and with the regional “normal” field model of Bulgaria to evaluate the success of the made predictions for the secular geomagnetic variations.KeywordsGeomagnetic fieldGeomagnetic modelsBulgaria