Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Center-limb dependence of photospheric velocities in regions of emerging
  magnetic fields on the Sun   We investigate the ratio of the vertical and horizontal velocities of the
photospheric plasma flows in the region of emerging magnetic fields on the Sun.
We carried out a study of photospheric velocities during the first hours of the
appearance of 83 active regions with magnetic flux more than 10^21 Mx with data
acquired by the Michelson Doppler Imager (MDI) on board the Solar and
Heliospheric Observatory (SOHO). The emerging magnetic fluxes under
investigation were isolated from extended concentrations of existing magnetic
fields; they have different spatial scales and are located at different
distances from the solar disk center. We found that the values of maximum
negative Doppler velocities that accompany the emergence of active region
magnetic fields during the first 12 hours increase nonlinearly with the
heliocentric angle. This result shows that the horizontal photospheric
velocities of plasma outflows are higher than the vertical ones of the plasma
upflows during the first hours of the emergence of active regions. The
horizontal velocity component at the site of emerging active regions exceeds
that of convective flows in the quiet Sun. A comparison between the velocities
and the maximum value of the total magnetic flux has not revealed any relation.

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The categories of this paper are: math
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The categories of this paper are: plasm-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: nlin
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The categories of this paper are: dg-ga
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The categories of this paper are: math-ph
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The categories of this paper are: solv-int
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The categories of this paper are: adap-org
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The categories of this paper are: hep-lat
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The categories of this paper are: gr-qc
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The categories of this paper are: quant-ph
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The categories of this paper are: q-fin
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The categories of this paper are: acc-phys
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The categories of this paper are: ao-sci
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The categories of this paper are: chem-ph