Development of geomagnetic field induction module maps for the territory of Ukraine

Abstract

Knowledge of Ukraine`s geomagnetic field is based on magnetic surveys of the geomagnetic field induction module B and its power and angular components, as well as on observations or calculations of their anomalous values. The article describes the methods for constructing a digital map of the induction module of the geomagnetic field B. The map of module B for the epoch of 1969.5 is developed, which is the ground to create the maps of module B and its anomalies ΔB for an arbitrary epoch. The results of the ground absolute magnetic survey of 1969-1972, the analytical model of the main geomagnetic field BIGRF, as well as the map of the anomalous magnetic field on a scale of 1: 1,000,000 were used to construct the map of the geomagnetic field induction module B. The digital map of the module and anomalies of the geomagnetic field induction module B for the 1969.5 epoch was obtained by calculating the correction based on their difference values at the points of the absolute reference network. It was spread by interpolation according to the 1x1km matrix to the entire data array for the territory of Ukraine. The geomagnetic field induction module B for the 2005.5 epoch was calculated by adding to its values in the 1969.5 epoch the calculated values of the field dynamics ВIGRF and the "magnetizing" effect of anomalies of the induction module ΔΔB. The developed map is an approximate representation of the magnetic field modulus, since the amount of remanent magnetization was not taken into account during the calculation, which may cause minor deviations of the calculated and observed field values. The induction module of the geomagnetic field B in the epoch of 1969.5 varies in the range of 46,500÷62,000 nT, and in the epoch of 2005.5 ‒ 47,000÷63000 nT, increasing from the southwest to the northeast of the territory of Ukraine. Its maximum values are observed in the areas of regional and local magnetic anomalies, in particular in the area of the Kryvyi Rih-Kremenchuk anomalous strip and the southeastern edge of the Kursk anomaly. The dynamics of the BIGRF field for the period of 1969.5÷2005.5 is characterized by values from 700 nT in the east of the territory of Ukraine to 950 nT in the west, and the magnitude of the magnetizing effect ΔΔB varies within ±10 nT, reaching maximum values (up to 100-190 nT) in the regions of intense magnetic anomalies. The digital map of the geomagnetic field induction module B, developed in 2005.5, has been verified. This was done by measuring the values of module B in the magnetic observatories of Kyiv, L’viv, and Odesa, as well as in the Repeat Stations of the Ist and IInd classes. The results showed that there was only a small difference (-20 ÷ 40 nT) between the calculated and measured values of modulus B. Their most significant differences are spatially correlated with areas of modern activation of the Earth's crust on the territory of Ukraine and electrical conductivity anomalies.