Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Comparison Between Turbulent Helical Dynamo Simulations and a Nonlinear
  Three-Scale Theory   Progress toward understanding principles of nonlinear growth and saturation
of large scale magnetic fields has emerged from comparison of theoretical
models that incorporate the evolution of magnetic helicity with numerical
simulations for problems that are more idealized than expected in astrophysical
circumstances, but still fully non-linear. We carry out a new comparison of
this sort for the magnetic field growth from forced isotropic helical
turbulence in a periodic box. Previous comparisons be- tween analytic theory
and simulations of this problem have shown that a two-scale model compares well
with the simulations in agreeing that the driver of large scale field growth is
the difference between kinetic and current helicities associated with the small
scale field, and that the backreaction that slows the growth of the large scale
field as the small scale current helicity grows. However, the two-scale model
artificially re- stricts the small scale current helicity to reside at the same
scale as the driving kinetic helicity. In addition, previous comparisons have
focused on the late time saturation regime, and less on the early-time growth
regime. Here we address these issues by comparing a three scale model to new
simulations for both early and late time growth regimes. We find that the
minimalist extension to three scales provides a better model for the field
evolution than the two-scale model because the simulations show that the small
scale current helicity does not reside at the same scale as that of the driving
kinetic helicity. The simulations also show that the peak of the small scale
current helicity migrates toward lower wave numbers as the growth evolves from
the fast to saturated growth regimes.

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The categories of this paper are: gr-qc
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The categories of this paper are: dg-ga
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The categories of this paper are: hep-lat
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The categories of this paper are: quant-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: adap-org
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ex
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The categories of this paper are: alg-geom
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The categories of this paper are: ao-sci
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The categories of this paper are: comp-gas
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The categories of this paper are: econ
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The categories of this paper are: cmp-lg
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The categories of this paper are: math-ph