Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The root of a comet tail - Rosetta ion observations at comet
  67P/Churyumov--Gerasimenko   The first 1000 km of the ion tail of comet 67P/Churyumov-Gerasimenko were
explored by the European Rosetta spacecraft, 2.7 au away from the Sun. We
characterised the dynamics of both the solar wind and the cometary ions on the
night-side of the comet's atmosphere. We analysed in situ ion and magnetic
field measurements and compared the data to a semi-analytical model. The
cometary ions are observed flowing close to radially away from the nucleus
during the entire excursion. The solar wind is deflected by its interaction
with the new-born cometary ions. Two concentric regions appear, an inner region
dominated by the expanding cometary ions and an outer region dominated by the
solar wind particles. The single night-side excursion operated by Rosetta
revealed that the near radial flow of the cometary ions can be explained by the
combined action of three different electric field components, resulting from
the ion motion, the electron pressure gradients, and the magnetic field
draping. The observed solar wind deflection is governed mostly by the motional
electric field.

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The categories of this paper are: bayes-an
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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: hep-th
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The categories of this paper are: econ
3
The categories of this paper are: physics
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The categories of this paper are: stat
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The categories of this paper are: alg-geom
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The categories of this paper are: plasm-ph
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The categories of this paper are: math
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The categories of this paper are: dg-ga
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The categories of this paper are: patt-sol
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The categories of this paper are: nucl-th
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The categories of this paper are: cond-mat
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The categories of this paper are: q-bio
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The categories of this paper are: q-alg