PhD defence: From Individual Magnetic Carriers to Global Magnetic Models Improving the Efficiency and Accuracy of Micromagnetic Tomography

The Earth's magnetic field is constantly changing. This is reflected in phenomena such as geomagnetic pole reversals and local anomalies, like the South Atlantic Anomaly, which affects technologies like satellites and navigation systems. To monitor the magnetic field, scientists use satellites. However, to understand changes in the distant past, we rely on natural "recorders" in rocks: iron-bearing minerals that capture the magnetic field during the solidification of volcanic rock. This process is similar to a compass needle being "frozen" in time.

By studying oriented rock samples in paleomagnetic laboratories, we can "read" these minerals and reconstruct the magnetic field from the past. Lava samples contain millions of magnetic minerals in different shapes and sizes, and by measuring them together, we can determine the strength and direction of the magnetic field at the time of solidification. However, the variety of minerals makes interpreting the results complex, as mineral properties such as volume and shape determine whether the magnetic field was accurately recorded.

With a new technique called Micromagnetic Tomography (MMT), we can measure the individual "compass needles" of minerals in a rock sample by combining high-resolution magnetic field measurements with NanoCT data. In my thesis, I describe the mathematical aspects of this technique and develop a statistical framework to interpret the results. Based on this framework, future studies can use Micromagnetic Tomography to select minerals that most accurately record the magnetic field. By combining this data with information from other locations and time periods, we can gain a better understanding of the origin and evolution of the Earth's magnetic field.