Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Investigating the Dynamics and Density Evolution of Returning Plasma
  Blobs from the 2011 June 7 Eruption   This work examines infalling matter following an enormous Coronal Mass
Ejection (CME) on 2011 June 7. The material formed discrete concentrations, or
blobs, in the corona and fell back to the surface, appearing as dark clouds
against the bright corona. In this work we examined the density and dynamic
evolution of these blobs in order to formally assess the intriguing morphology
displayed throughout their descent. The blobs were studied in five wavelengths
(94, 131, 171, 193 and 211 \AA) using the Solar Dynamics Observatory
Atmospheric Imaging Assembly (SDO/AIA), comparing background emission to
attenuated emission as a function of wavelength to calculate column densities
across the descent of four separate blobs. We found the material to have a
column density of hydrogen of approximately 2 $\times$ 10$^{19}$ cm$^{-2}$,
which is comparable with typical pre-eruption filament column densities.
Repeated splitting of the returning material is seen in a manner consistent
with the Rayleigh-Taylor instability. Furthermore, the observed distribution of
density and its evolution are also a signature of this instability. By
approximating the three-dimensional geometry (with data from STEREO-A),
volumetric densities were found to be approximately 2 $\times$ 10$^{-14}$ g
cm$^{-3}$, and this, along with observed dominant length-scales of the
instability, was used to infer a magnetic field of the order 1 G associated
with the descending blobs.

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The categories of this paper are: q-alg
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The categories of this paper are: bayes-an
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The categories of this paper are: alg-geom
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The categories of this paper are: mtrl-th
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The categories of this paper are: cond-mat
3
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: chem-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: dg-ga
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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: chao-dyn
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
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The categories of this paper are: stat