Generation of large-scale magnetic fields by small-scale dynamo in shear flows
Authors: J. Squire and A. Bhattacharjee
Abstract: We propose a new mechanism for turbulent
mean-field dynamo in which the magnetic fluctuations resulting
from a small-scale dynamo drive the generation of large-scale
magnetic fields. This is in stark contrast to the common idea that
small-scale magnetic fields should be harmful to large-scale
dynamo action. These dynamos occur in the presence of large-scale
velocity shear and do not require net helicity, resulting from
o ff-diagonal components of the turbulent resistivity tensor as
the magnetic analogue of the shear-current eff ect. Given the
inevitable existence of non-helical small-scale magnetic fields in
turbulent plasmas, as well as the generic nature of velocity
shear, the suggested mechanism may help to explain generation of
large-scale magnetic fields across a wide range of astrophysical
objects.
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Submitted to: Physical Review Letters
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PPPL-5148 (pdf 2.9 MB 13 pp)
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