Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Revisiting linear dynamics of non-axisymmetric perturbations in weakly
  magnetized accretion discs   We investigate linear dynamics of non-axisymmetric perturbations in
incompressible, vertically stratified Keplerian discs with a weak vertical
magnetic field in the shearing box approximation. Perturbations are decomposed
into shearing waves whose evolution is followed via numerical integration of
the linearized ideal MHD equations. There are two basic modes in the system --
inertia-gravity waves and magnetic mode, which displays the magnetorotational
instability (MRI). As distinct from previous studies, we introduce
`eigenvariables' characterizing each (counter-propagating) component of the
inertia-gravity and magnetic modes, which are governed by a set of four first
order coupled ordinary differential equations. This allowed us to identify a
new process of linear coupling of the two above non-axisymmetric modes due to
the disc's differential rotation. We did a comparative analysis of the dynamics
of non-axisymmetric and axisymmetric magnetic mode perturbations. It is shown
that the growth of optimal and close-to-optimal non-axisymmetric harmonics of
this mode, having transient nature, can prevail over the exponential growth of
axisymmetric ones (i.e., over the axisymmetric MRI) during dynamical time. A
possible implication of this result for axisymmetric channel solutions is
discussed. Specifically, the formation of the channel may be affected/impeded
by non-axisymmetric modes already at the early linear stage leading to its
untimely disruption -- the outcome strongly depends on the amplitude and
spectrum of initial perturbation. So, this competition may result in an
uncertainty in the magnetic mode's non-linear dynamics. It is also shown that a
maximum non-axisymmetric growth is at vertical wavelengths close to the
scale-height for which compressibility effects are important. This indirectly
suggests that compressibility plays a role in the dynamics of the
non-axisymmetric MRI.

21
The categories of this paper are: adap-org
29
The categories of this paper are: funct-an
7
The categories of this paper are: hep-th
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
20
The categories of this paper are: acc-phys
9
The categories of this paper are: nlin
36
The categories of this paper are: cmp-lg
13
The categories of this paper are: quant-ph
24
The categories of this paper are: dg-ga
28
The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
2
The categories of this paper are: math
8
The categories of this paper are: hep-ex