Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the fine structure of the sunspot penumbrae. III The vertical
  extension of penumbral filaments   In this paper we study the fine structure of the penumbra as inferred from
the uncombed model (flux tube embedded in a magnetic surrounding) when applied
to penumbral spectropolarimetric data from the neutral iron lines at 6300 \AA.
The inversion infers very similar radial dependences in the physical quantities
(LOS velocity, magnetic field strength etc) as those obtained from the
inversion of the Fe I 1.56 $\mu$m lines. In addition, the large Stokes $V$ area
asymmetry exhibited by the visible lines helps to constrain the size of the
penumbral flux tubes. As we demonstrate here, the uncombed model is able to
reproduce the area asymmetry with striking accuracy, returning flux tubes as
thick as 100-300 kilometers in the vertical direction, in good agreement with
previous investigations.

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The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
36
The categories of this paper are: cmp-lg
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The categories of this paper are: acc-phys
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The categories of this paper are: dg-ga
22
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: comp-gas
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The categories of this paper are: q-alg
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The categories of this paper are: stat
18
The categories of this paper are: econ
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The categories of this paper are: cs
19
The categories of this paper are: eess
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The categories of this paper are: hep-ph
15
The categories of this paper are: nucl-ex