Walter Maurice Elsasser (March 20, 1904 – October 14, 1991) was a German-born American physicist, a developer of the presently accepted dynamo theory as an explanation of the Earth's magnetism.

[2] This suggestion of Elsasser was later communicated by his senior colleague from Göttingen (Nobel Prize recipient Max Born) to physicists in England.

Eugene Wigner, J. Hans D. Jensen and Maria Goeppert-Mayer received the Nobel in 1963 for work developing out of Elsasser's initial formulation.

He conjectured that it could be a self-sustaining dynamo, powered by convection in the liquid outer core, and described a possible feedback mechanism between flows having two different geometries, toroidal and poloidal (indeed, inventing the terms).

[5][6][7][8][9][10][11] The final version of his thoughts on this subject can be found in his book Reflections on a Theory of Organisms, published in 1987 and again posthumously with a new foreword by Harry Rubin in 1998.

[4][20] In 1987, he was awarded the USA's National Medal of Science "for his fundamental and lasting contributions to physics, meteorology, and geophysics in establishing quantum mechanics, atmospheric radiation transfer, planetary magnetism and plate tectonics.