Here Carl Friedrich Gauss researched geomagnetism.
Historical Earthquake Station | Gauss house and earth magnetism
Gauss test and geomagnetic field
In addition to theoretical fundamentals of the geomagnetic field, Gauss has also developed a method for determining the horizontal intensity H. This “Gauss test” became a model for many precision measurements of physics. The basic idea is the simultaneous determination of H and the magnetic moment M of a sample magnet in two separate experiments: In the “vibration test” M x H and in the “deflection test” M / H is determined. From the results of both experiments M and H can be calculated individually. From H and the deviations of a compass needle from the geographic north direction (declination) and from the horizontal plane (inclination), one could accurately determine the earth’s magnetic field for any location in the world, using only the known cgs units grams, seconds and centimeters. Therefore today we know that the earth’s magnetic field has decreased by about 10% in the last 180 years. It is believed that the Earth’s magnetic field is currently reversing. On average, this event takes place every 250,000 years. The cause of the earth’s magnetic field is convection currents in the outer liquid core (geodynamo).
In the Gaußhaus there is now an apparatus with which the Gauss test can be carried out.