Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Magnetic Turbulence and Thermodynamics in the Inner Region of
  Protoplanetary Discs   Using radiation magnetohydrodynamics simulations with realistic opacities and
equation of state, and zero net magnetic flux, we have explored thermodynamics
in the inner part of protoplanetary discs where magnetic turbulence is
expected. The thermal equilibrium curve consists of the upper, lower, and
middle branches. The upper (lower) branch corresponds to hot (cool) and
optically very (moderately) thick discs, respectively, while the middle branch
is characterized by convective energy transport near the midplane. Convection
is also the major energy transport process near the low surface density end of
the upper branch. There, convective motion is fast with Mach numbers reaching
$\gtrsim 0.01$, and enhances both magnetic turbulence and cooling, raising the
ratio of vertically-integrated shear stress to vertically-integrated pressure
by a factor of several. This convectively enhanced ratio seems a robust feature
in accretion discs having an ionization transition. We have also examined
causes of the S-shaped thermal equilibrium curve, as well as the thermal
stability of the equilibrium solutions. Finally, we compared our results with
the disc instability models used to explain FU Ori outbursts. Although the
thermal equilibrium curve in our results also exhibits bistability, the surface
density contrast across the bistability is an order of magnitude smaller, and
the stress-to-pressure ratios in both upper and lower branches are two orders
of magnitude greater, than those favored in the disc instability models. It
therefore appears likely that FU Ori outbursts are not due solely to a
thermal-viscous limit cycle resulting from accretion driven by local magnetic
turbulence.

16
The categories of this paper are: stat
10
The categories of this paper are: q-bio
19
The categories of this paper are: eess
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
33
The categories of this paper are: plasm-ph
37
The categories of this paper are: supr-con
30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph
18
The categories of this paper are: econ
23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex