Jean-Louis Le Mouël

Jean-Louis Le Mouël was awarded the first Shen Kuo medal for outstanding contributions to geomagnetism over his long and distinguished career. Through his combination of observational and theoretical work at Chambon-La Forêt magnetic observatory and at IPGP, we have a much wider and more readily accessible suite of geomagnetic measurements, and a better understanding of the dynamical processes operating in the Earth's core responsible for the geodynamo, and of the electrical characteristics of the Earth's mantle.

Jean-Louis was instrumental in establishing the extensive French geomagnetic observatory network and in encouraging regional magnetic surveying (including aeromagnetic surveys), data sources which have been crucial to the international community, both research and exploration, over so many years. He was a key figure in establishing the worldwide INTERMAGNET geomagnetic observatory network, and associated data standards. He encouraged electromagnetic investigation of tectonically and volcanically active regions in areas of French influence world-wide. He has played a prominent rôle in the space age, through initiating a collaboration that led to the construction of the absolute magnetometers on board the Ørsted and CHAMP satellites; the success of these missions set the stage for the satellite constellation Swarm.

Amongst his major scientific achievements, the discovery of geomagnetic 'jerks' or impulses is probably the best known. Their origin remains enigmatic, but they have implications for core dynamics, core-mantle coupling, and the electrical conductivity of the mantle, all areas in which Jean-Louis and colleagues have made significant contributions. He introduced a dynamic constraint - tangential geostrophy - on the outer core fluid at the core-mantle boundary, which has been a crucial component of using the geomagnetic secular variation as a tracer of the flow. The flows deduced predict the decadal timescale changes in length-of-day, an independent data set, through angular momentum exchange between the core and mantle.

Besides his contributions to geomagnetism through fundamental developments in observations and theory, as evidenced by >230 publications cited almost 5000 times, Jean-Louis has served the geomagnetism (and wider geoscientific) community, nationally and internationally, with exceptional dedication. Besides his leadership of IPGP, he was instrumental in the establishment of the IUGG Studies of the Earth's Deep Interior commission, and served a term as its Chair. He has also supervised and mentored a large number of young scientists, many of whom are now senior members of the geomagnetism community.