We wanted to make a satellite altitude magnetic anomaly map of the large magnetic anomaly in the Central African Republic, the Bangui magnetic anomaly, with data from the Swarm satellites. In the first part of our study, we summarize the earlier investigations and their interpretation. In the second we discuss our data processing applied to produce a magnetic anomaly map. We used the IGRF 12 th to remove the long-wavelength regional anomalies. We will use an inverse procedure, which always requires a solution of the direct problem, and a horizontal polygonal prism given in the Descartes coordinate system. For this, reason the total magnetic anomaly was transformed into the Descartes coordinate system. The magnetization and its direction were used from our previous paper. The inverse problem is solved by the Simplex procedure. Our selected polygon has 14 geometrical parameters however, the inverse problem that is the numerical determination of the minimum problem is solved in the 14 dimensions. The result of our inverse problem was the 12 horizontal coordinates and the two upper and lower data of the polygon. The origin of the Bangui anomaly has been discussed in several scientific reports, either as a deep crustal tectonic feature or the result of a large external impactor. However, according to our inversion computations we cannot make any unambiguous finding for the origin of this feature. The inaccuracy in our total anomaly map is given by the Gaussian error propagation.
We computed magnetic field gradients at satellite altitude, over Europe with emphasis on the Kursk Magnetic Anomaly (KMA). They were calculated using the CHAMP satellite total magnetic anomalies. Our computations were done to determine how the magnetic field observations data from the new ESA/Swarm satellites could be utilized to determine the structure of the magnetization of the Earth's crust, especially in the region of the KMA. Ten years of CHAMP data were used to simulate the Swarm data. An initial east magnetic anomaly gradient map of Europe was computed and subsequently the North, East and Vertical magnetic gradients for the KMA region were calculated. The vertical gradient of the KMA was also determined using Hilbert transforms. Inversion of the total KMA was derived using Simplex and Simulated Annealing algorithms. The depths of the upper and lower boundaries are calculated downward from the 324 km elevation of the satellite. Our resulting inversion depth model is a horizontal quadrangle. The maximum errors are determined by the model parameter errors.
Our paper discusses the determination of total magnetic field anomalies derived from the Swarm-A satellite data; one of two low orbiting satellites of the three Swarm formations. This procedure requires several modifications. The first step is the conversion of the measured CDF data to the ASCII format. This step is followed for the selection of the data with K p index ≤ 1 +. The anomalies are determined by the removal of the IGRF from the resulting satellite data. There are two Swarm-A data sets descending (6000) orbits and ascending (5688) orbits. For our study the descending orbits were used. The calculations next step is to difference of the two-dimensional linear field Figure 3 fitted to the Swarm-A anomalies and the anomalies given in Figure 2. These anomalies are filtered by Gaussian low-pass filter. The last step of the corrections is the remove the direct component, zero spatial frequency, from the descending orbits. The anomalies and their vertical gradients are qualitatively interpreted over Central Europe and the Pannonian Basin.
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