Walter M. Elsasser

Walter Maurice Elsasser was a German born American physicist, born in 1904 in Mannheim, Germany, and died in 1991 in Baltimore, Maryland. He developed the dynamo theory now accepted to explain the origin of Earth's magnetic field, proposing that electric currents circulating in the planet's fluid outer core generate it, and he showed how the history of that field is recorded in the magnetic orientation of minerals within rocks, work foundational to the study of paleomagnetism.