Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Radio and optical observations of large-scale traveling ionospheric
  disturbances during a strong geomagnetic storm of 6-8 April 2000   Basic properties of the mid-latitude large-scale traveling ionospheric
disturbances (LS TIDs) during the maximum phase of a strong magnetic storm of
6-8 April 2000 are shown. Total electron content (TEC) variations were studied
by using data from GPS receivers located in Russia and Central Asia. The
nightglow response to this storm at mesopause and termospheric altitudes was
also measured by optical instruments FENIX located at the observatory of the
Institute of Solar-Terrestrial Physics, (51.9 deg. N, 103.0 deg. E) and MORTI
located at the observatory of the Institute of Ionosphere (43.2 deg. N, 77.0
deg. E). Observations of the O (557.7 nm, 630.0 nm, 360-410 nm, and 720-830 nm)
emissions originating from atmospheric layers centered at altitudes of 90 km,
97 km, and 250 km were carried out at Irkutsk and of the O_2 (866.5 nm)
emission originating from an atmospheric layer centered at altitude of 95 km
was carried out at Almaty. Variations of the f_0F2 and virtual altitude of the
F2 layer were measured at Almaty as well. An analysis of data was performed for
the time interval 17.00-21.00 UT comprising a maximum of the Dst derivative.
Results have shown that the storm-induced solitary large-scale wave with
duration of 1 hour and with the front width of 5000 km moved equatorward with
the velocity of 200 ms-1 to a distance of no less than 1000 km. The TEC
disturbance, basically displaying an electron content depression in the maximum
of the F2 region, reveals a good correlation with growing nightglow emission,
the temporal shift between the TEC and emission variation maxima being
different for different altitudes.

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The categories of this paper are: gr-qc
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The categories of this paper are: q-bio
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The categories of this paper are: atom-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: chem-ph
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The categories of this paper are: eess
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The categories of this paper are: nucl-th
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The categories of this paper are: adap-org
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The categories of this paper are: hep-lat
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The categories of this paper are: acc-phys
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The categories of this paper are: supr-con
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The categories of this paper are: math
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The categories of this paper are: nlin
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The categories of this paper are: astro-ph
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The categories of this paper are: stat
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The categories of this paper are: plasm-ph