Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Two types of axisymmetric helical magnetorotational instability in
  rotating flows with positive shear   We reveal and investigate a new type of linear axisymmetric helical
magnetorotational instability which is capable of destabilizing viscous and
resistive rotational flows with radially increasing angular velocity, or
positive shear. This instability is double-diffusive by nature and is different
from the more familiar helical magnetorotational instability, operating at
positive shear above the Liu limit, in that it works instead for a wide range
of the positive shear when ${\rm (i)}$ a combination of axial/poloidal and
azimuthal/toroidal magnetic fields is applied and ${\rm (ii)}$ the magnetic
Prandtl number is not too close to unity. We study this instability first with
radially local WKB analysis and then confirm its existence using a global
stability analysis of the magnetized flow between two rotating cylinders with
conducting or insulating boundaries. From an experimental point of view, we
also demonstrate the presence of the new instability in a magnetized viscous
and resistive Taylor-Couette flow with positive shear for such values of the
flow parameters, which can be realized in upcoming experiments at the DRESDYN
facility. Finally, this instability might have implications for the dynamics of
the equatorial parts of the solar tachocline and dynamo action there, since the
above two necessary conditions for the instability to take place are satisfied
in this region. Our global stability calculations for the tachocline-like
configuration, representing a thin rotating cylindrical layer with the
appropriate boundary conditions -- conducting inner and insulating outer
cylinders -- and the values of the flow parameters, indicate that it can indeed
arise in this case with a characteristic growth time comparable to the solar
cycle period.

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The categories of this paper are: stat
2
The categories of this paper are: math
25
The categories of this paper are: patt-sol
7
The categories of this paper are: hep-th
35
The categories of this paper are: mtrl-th
15
The categories of this paper are: nucl-ex
31
The categories of this paper are: ao-sci
37
The categories of this paper are: supr-con
5
The categories of this paper are: gr-qc
33
The categories of this paper are: plasm-ph
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
1
The categories of this paper are: cs
22
The categories of this paper are: chao-dyn
26
The categories of this paper are: bayes-an
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The categories of this paper are: q-fin