Observation of magnetism aims at understanding the origins of magnetic field variations at different temporal and spacial scales.

EOST runs six permanent magnetic stations located in the French Austral, Antarctic Territories and Madagascar Island. They are part of two networks:  Bureau Central de magnétisme terrestre (BCMT) and INTERMAGNET (INTERnational Real-time MAGnetic observatory NETwork). EOST is also the headquarter of International Service of Intermagnetic Indices (ISGI).