Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Fossil magnetic field of accretion disks of young stars   We elaborate the model of accretion disks of young stars with the fossil
large-scale magnetic field in the frame of Shakura and Sunyaev approximation.
Equations of the MHD model include Shakura and Sunyaev equations, induction
equation and equations of ionization balance. Magnetic field is determined
taking into account ohmic diffusion, magnetic ambipolar diffusion and buoyancy.
Ionization fraction is calculated considering ionization by cosmic rays and
X-rays, thermal ionization, radiative recombinations and recombinations on the
dust grains.
  Analytical solution and numerical investigations show that the magnetic field
is coupled to the gas in the case of radiative recombinations. Magnetic field
is quasi-azimuthal close to accretion disk inner boundary and quasi-radial in
the outer regions.
  Magnetic field is quasi-poloidal in the dusty "dead" zones with low
ionization degree, where ohmic diffusion is efficient. Magnetic ambipolar
diffusion reduces vertical magnetic field in 10 times comparing to the
frozen-in field in this region. Magnetic field is quasi-azimuthal close to the
outer boundary of accretion disks for standard ionization rates and dust grain
size a_d=0.1 micrometers. In the case of large dust grains (a_d > 0.1
micrometers) or enhanced ionization rates, the magnetic field is quasi-radial
in the outer regions.
  It is shown that the inner boundary of dusty "dead" zone is placed at
r=(0.1-0.6) AU for accretion disks of stars with M=(0.5-2) M_{\odot}. Outer
boundary of "dead" zone is placed at r=(3-21) AU and it is determined by
magnetic ambipolar diffusion. Mass of solid material in the "dead" zone is more
than 3 M_{\oplus} for stars with M \geq 1 M_{\odot}.

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The categories of this paper are: patt-sol
37
The categories of this paper are: supr-con
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
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The categories of this paper are: chao-dyn
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The categories of this paper are: nlin
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The categories of this paper are: hep-lat
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The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
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The categories of this paper are: bayes-an
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The categories of this paper are: comp-gas
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The categories of this paper are: solv-int
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The categories of this paper are: cmp-lg
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-ex
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The categories of this paper are: plasm-ph