Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dayside magnetospheric and ionospheric responses to a foreshock
  transient on June 25, 2008: 2. 2-D evolution based on dayside auroral imaging   The foreshock region involves localized and transient structures such as
foreshock cavities and hot flow anomalies due to solar wind-bow shock
interactions, and foreshock transients have been shown to lead to
magnetospheric and ionospheric responses. In this paper, the interaction
between a foreshock transient and the magnetosphere-ionosphere system is
investigated using dayside aurora imagers revealing structures and propagation
in greater detail than previously possible. A foreshock transient was detected
by THEMIS-B and C during 1535-1545 UT on June 25, 2008. THEMIS-A, D and E
observed magnetopause compression, cold plasma enhancement and ULF waves in the
dayside magnetosphere. The all-sky imager (ASI) at South Pole observed that
both diffuse and discrete aurora brightened locally soon after the appearance
of this foreshock transient. The diffuse aurora brightening, which corresponded
to a region a few Re size in GSM-Y in the equatorial plane, propagated duskward
with an average speed of ~100 km/s. Soon after the diffuse aurora brightened,
discrete aurora also brightened and extended duskward, which was consistent
with the motion of the foreshock transient as it swept through the
magnetosheath while impacting the magnetopause. Equivalent horizontal currents
measured by magnetometers revealed a pair of field-aligned currents (FACs)
moving duskward consistent with motion of the discrete aurora patterns. We
conclude that the high-resolution and two-dimensional observation of auroral
responses by ground-based ASI can help to estimate the evolution and
propagation of upstream foreshock transients and their substantial impacts on
the magnetosphere-ionosphere coupling system, including magnetospheric
compression and currents in the ionosphere.

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The categories of this paper are: cond-mat
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The categories of this paper are: hep-ph
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The categories of this paper are: q-alg
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The categories of this paper are: chem-ph
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The categories of this paper are: q-bio
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The categories of this paper are: nucl-th
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The categories of this paper are: quant-ph
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The categories of this paper are: math
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The categories of this paper are: adap-org
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The categories of this paper are: cs
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The categories of this paper are: nucl-ex
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: bayes-an
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The categories of this paper are: econ