Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Radiation Magneto-hydrodynamic Simulations of the Formation of Hot
  Accretion Disk Coronae   A new mechanism to form a magnetic pressure supported, high temperature
corona above the photosphere of an accretion disk is explored using three
dimensional radiation magneto-hydrodynamic (MHD) simulations. The thermal
properties of the disk are calculated self-consistently by balancing radiative
cooling through the surfaces of the disk with heating due to dissipation of
turbulence driven by magneto-rotational instability (MRI). As has been noted in
previous work, we find the dissipation rate per unit mass increases
dramatically with height above the mid-plane, in stark contrast to the
alpha-disk model which assumes this quantity is a constant. Thus, we find that
in simulations with a low surface density (and therefore a shallow
photosphere), the fraction of energy dissipated above the photosphere is
significant (about 3.4% in our lowest surface density model), and this fraction
increases as surface density decreases. When a significant fraction of the
accretion energy is dissipated in the optically thin photosphere, the gas
temperature increases substantially and a high temperature, magnetic pressure
supported corona is formed. The volume-averaged temperature in the disk corona
is more than 10 times larger than at the disk mid-plane. Moreover, gas
temperature in the corona is strongly anti-correlated with gas density, which
implies the corona formed by MRI turbulence is patchy. This mechanism to form
an accretion disk corona may help explain the observed relation between the
spectral index and luminosity from AGNs, and the soft X-ray excess from some
AGNs. It may also be relevant to spectral state changes in X-ray binaries.

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The categories of this paper are: bayes-an
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The categories of this paper are: patt-sol
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The categories of this paper are: math-ph
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The categories of this paper are: math
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The categories of this paper are: comp-gas
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The categories of this paper are: gr-qc
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The categories of this paper are: q-fin
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The categories of this paper are: chem-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: supr-con
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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
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The categories of this paper are: nucl-th
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The categories of this paper are: adap-org
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-ex