Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Effect of Fractional Kinetic Helicity on Turbulent Magnetic Dynamo
  Spectra   Magnetic field amplification in astrophysics ultimately requires an
understanding of magnetohydrodynamic turbulence. Kinetic helicity has long been
known to be important for large scale field growth in forced MHD turbulence,
and has been recently demonstrated numerically to be asymptotically consistent
with slow mean field dynamo action in a periodic box. Here we show numerically
that the magnetic spectrum at and below the forcing scale is also strongly
influenced by kinetic helicity. We identify a critical value, $f_{h,crit}$
above which the magnetic spectrum develops maxima at wavenumber $= 1$ scale
{\it and} at the forcing scale, For $f< f_{h,crit}$ the field peaks only at the
resistive scale. Kinetic helicity may thus be important not only for generating
a large scale field, but also for establishing observed peaks in magnetic
spectra at the forcing scale. The turbulent Galactic disk provides an example
where both large scale ($>$ supernova forcing scale) fields and small scale
($\le$ forcing scale, with peak at forcing scale) fields are observed. We
discuss this, and the potential application to the protogalaxy, but also
emphasize the limitations in applying our results to these systems.

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The categories of this paper are: atom-ph
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The categories of this paper are: gr-qc
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The categories of this paper are: alg-geom
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The categories of this paper are: physics
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-ph
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The categories of this paper are: econ
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The categories of this paper are: math
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The categories of this paper are: adap-org
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The categories of this paper are: q-bio
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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The categories of this paper are: patt-sol
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The categories of this paper are: mtrl-th
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The categories of this paper are: nucl-th
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The categories of this paper are: dg-ga