Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Outbursts in Global Protoplanetary Disk Simulations   While accreting through a circumstellar disk, young stellar objects are
observed to undergo sudden and powerful accretion events known as FUor or EXor
outbursts. Although such episodic accretion is considered to be an integral
part of the star formation process, the triggers and mechanisms behind them
remain uncertain. We conducted global numerical hydrodynamics simulations of
protoplanetary disk formation and evolution in the thin-disk limit, assuming
both magnetically layered and fully magnetorotational instability (MRI)-active
disk structure. In this paper, we characterize the nature of the outbursts
occurring in these simulations. The instability in the dead zone of a typical
layered disk results in "MRI outbursts". We explore their progression and their
dependence on the layered disk parameters as well as cloud core mass. The
simulations of fully MRI-active disks showed an instability analogous to the
classical thermal instability. This instability manifested at two
temperatures--above approximately 1400 K and 3500 K--due to the steep
dependence of Rosseland opacity on the temperature. The origin of these
thermally unstable regions is related to the bump in opacity resulting from
molecular absorption by water vapor and may be viewed as a novel mechanism
behind some of the shorter duration accretion events. Although we demonstrated
local thermal instability in the disk, more investigations are needed to
confirm that a large-scale global instability will ensue. We conclude that the
magnetic structure of a disk, its composition, as well as the stellar mass, can
significantly affect the nature of episodic accretion in young stellar objects.

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The categories of this paper are: gr-qc
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The categories of this paper are: stat
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The categories of this paper are: cs
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The categories of this paper are: math
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The categories of this paper are: physics
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The categories of this paper are: hep-lat
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The categories of this paper are: q-alg
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The categories of this paper are: eess
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The categories of this paper are: nucl-th
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The categories of this paper are: math-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: cond-mat
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The categories of this paper are: q-bio
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The categories of this paper are: acc-phys
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The categories of this paper are: econ
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The categories of this paper are: hep-ph