ELSASSER, WALTER M.

Hydromagnetic Dynamo Theory.

Lancaster, American Physical Society, 1956. Lex8vo. Volume 28, April, No. 2, 1955 of "Reviews of Modern Physics". Entire volume in the original printed orange wrappers. Previous owner's name to upper margin of front wrapper. A 2 cm long tear to upper left corner of front wrapper. Otherwise a very nice and clean copy. [Elasser:] Pp. 135-163. [Entire issue: Pp. 103-170].

First printing of Elsasser's paper on the Hydromagnetic Dynamo Theory. Elsasser, considered the father of the presently accepted dynamo theory as an explanation of the Earth's magnetism, proposed that this magnetic field resulted from electric currents induced in the fluid outer core of the Earth. He revealed the history of the Earth's magnetic field through pioneering the study of the magnetic orientation of minerals in rocks.

"His [Elsasser] main attention became focused on a research field he had been cultivating almost as a diversion alongside his official duties since the late 1930s: geomagnetism. Discounting a hypothesis popularized by Einstein and Patrick Maynard Stuart Blackett that Earth's magnetic field is a property of its rotation per se, he thought instead of a self-sustaining dynamo in the molten metallic core. A key clue for Elsasser in his approach to the problem was a similarity between maps of the long-term variations in Earth's magnetic field and the maps of atmospheric flows familiar from his work in meteorology. Elsasser theorized that Coriolis forces and convection currents in the conductive liquid combined to produce poloidal magnetic and toroidal electric fields (the former extending beyond Earth's surface, the latter interior to it) that had a feedback effect on each other. Though some details were unclear, he argued that the dynamo theory gave the right order of magnitude for the magnetic field's strength and potentially accounted for its secular variations. By the mid-1950s, Elsasser's junior colleague at Utah, Eugene Newman Parker, and the British physicists Edward Crisp Bullard and the Australian-born George Keith Batchelor had explored alternative dynamo models and elaborated the mathematics showing that the field was self-sustaining. The dynamo theory ultimately received wide acceptance. It subsequently also became a key element of Hannes Alfvén's Nobel Prize-winning work on plasma electrodynamics. In the 1960s, Elsasser's geophysical interests moved into modeling seismic deformation in the context of the burgeoning theory of plate tectonics." (DSB)

Order-nr.: 45136