Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic field amplification by the r-mode instability   We discuss magnetic field enhancement by unstable r-modes (driven by the
gravitational radiation reaction force) in rotating stars. In the absence of a
magnetic field, gravitational radiation exponentially increases the r-mode
amplitude $\alpha$, and accelerates differential rotation (secular motion of
fluid elements). For a magnetized star, differential rotation enhances the
magnetic field energy. Rezzolla et al. (2000--2001) argued that if the magnetic
energy grows faster than the gravitational radiation reaction force pumps
energy into the r-modes, then the r-mode instability is suppressed. Chugunov
(2015) demonstrated that without gravitational radiation, differential rotation
can be treated as a degree of freedom decoupled from the r-modes and controlled
by the back reaction of the magnetic field. In particular, the magnetic field
windup does not damp r-modes. Here we discuss the effect of the back reaction
of the magnetic field on differential rotation of unstable r-modes, and show
that it limits the generated magnetic field and the magnetic energy growth rate
preventing suppression of the r-mode instability by magnetic windup at low
saturation amplitudes, $\alpha \ll 1$, predicted by current models.

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The categories of this paper are: dg-ga
19
The categories of this paper are: eess
1
The categories of this paper are: cs
10
The categories of this paper are: q-bio
36
The categories of this paper are: cmp-lg
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
14
The categories of this paper are: math-ph
37
The categories of this paper are: supr-con
26
The categories of this paper are: bayes-an
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
5
The categories of this paper are: gr-qc
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The categories of this paper are: alg-geom