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Dynamos driven by poloidal flow exist
Author(s) -
Love J. J.,
Gubbins David
Publication year - 1996
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/96gl00846
Subject(s) - dynamo , physics , dynamo theory , helicity , magnetic helicity , classical mechanics , solar dynamo , toroid , magnetic field , magnetic reynolds number , toroidal and poloidal , magnetohydrodynamics , dipole , quantum electrodynamics , mechanics , reynolds number , turbulence , plasma , quantum mechanics
We have discovered a class of dynamos driven by purely poloidal fluid motion, thereby demonstrating that toroidal motion is not essential for dynamo action and that there is no counterpart to the antidynamo theorem that purely toroidal motions cannot generate magnetic fields. The fully three‐dimensional (3D) dynamo action of these models results from the pushing and twisting of magnetic field lines by helical motion in a manner akin to the α² mechanism of mean‐field electrodynamics. No dynamo with dipole symmetry was found for an axisymmetric distribution of helicity; indeed, some azimuthal variation in helicity is required. Among the suite of dynamos that we have investigated, the poloidal flow dynamo with the smallest critical magnetic Reynolds number is very nearly the dynamo with the most nonaxisymmetric distribution of helicity.