Why all the effort?

Direct measurements of the Earth’s magnetic field are continuously made at magnetic observatories around the world, and are also obtained from a variety of sources, including oceanographic surveys, land-based surveys, aircraft, and even satellites. All of this data collection has led some to ask, "Why all the effort?" For me, there are two main reasons that stand out. First, very few physical quantities can provide a historical record that can be measured today. While studies of seismology and the Earth's gravity field have revealed many secrets about our planet’s interior, they do not offer a timeline through which we can observe how these measurements have changed over time. Measurements that can be examined retroactively are extremely valuable for making inferences about the Earth's past conditions. The second reason relates to the fact that the magnetic field we measure is not a single entity, but a combination of fields produced by different sources. The Earth's primary magnetic field is generated in the fluid outer core through a self-exciting dynamo process. In addition to the core field, the magnetic field observable at the Earth's surface is also influenced by sources in the crust, the ionosphere, and the magnetosphere. The geomagnetic field varies on a wide range of spatial and temporal scales, and these variations can now be described in both the space and time domains, from low-frequency to high-frequency changes. Earth’s magnetic field is highly dynamic, and its variations—particularly those linked to solar activity—can have significant effects on modern technology. For instance, geomagnetic disturbances can impact power grids, cause blackouts, and interfere with communication systems, such as radios and telephones.

Understanding and mapping these variations has been a central focus of my research, contributing to a large international effort aimed at improving our knowledge of Earth's magnetic field. In the following sections, I will provide a more detailed account of my work and explain why the study of planetary magnetic fields—such as those of Mars, Mercury, and Venus—is also of great interest to me. For more detailed information, my publications list provides further insights into this field of research.

Ancient magnetic data

Before the establishment of modern geomagnetic observatories and the development of absolute methods for measuring magnetic intensity (such as those introduced by Gauss in the 1830s), magnetic observations were made primarily by mariners engaged in merchant and naval shipping. These early observations, mostly focused on declination, extend the global dataset of magnetic field variations back to the early 16th century. As part of my research, I have discovered new sources of historical magnetic data and reviewed early attempts to describe the Earth's magnetic field, including the work of Nautonier (1602). This work led me to examine old books and maps, including measurements taken by the French Navy and some of the first geomagnetic maps. I have also conducted a study on magnetic field variations in Western Europe over the last few centuries, focusing on data from cities like Paris, London, Munich, and Bucharest.

Observatories

Other ground direct observations

Satellites