Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The interaction between transpolar arcs and cusp spots   Transpolar arcs and cusp spots are both auroral phenomena which occur when
the interplanetary magnetic field is northward. Transpolar arcs are associated
with magnetic reconnection in the magnetotail, which closes magnetic flux and
results in a "wedge" of closed flux which remains trapped, embedded in the
magnetotail lobe. The cusp spot is an indicator of lobe reconnection at the
high-latitude magnetopause; in its simplest case, lobe reconnection
redistributes open flux without resulting in any net change in the open flux
content of the magnetosphere. We present observations of the two phenomena
interacting--i.e., a transpolar arc intersecting a cusp spot during part of its
lifetime. The significance of this observation is that lobe reconnection can
have the effect of opening closed magnetotail flux. We argue that such events
should not be rare.

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The categories of this paper are: econ
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The categories of this paper are: q-alg
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The categories of this paper are: comp-gas
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The categories of this paper are: bayes-an
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The categories of this paper are: plasm-ph
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The categories of this paper are: chao-dyn
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The categories of this paper are: q-fin
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The categories of this paper are: nucl-th
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The categories of this paper are: math
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The categories of this paper are: q-bio
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The categories of this paper are: stat
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The categories of this paper are: hep-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: adap-org
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The categories of this paper are: nlin
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The categories of this paper are: acc-phys