Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Imaging Spectroscopy on Preflare Coronal Nonthermal Sources Associated
  with the 2002 July 23 Flare   We present a detailed examination on the coronal nonthermal emissions during
the preflare phase of the X4.8 flare that occurred on 2002 July 23. The
microwave (17 GHz and 34 GHz) data obtained with Nobeyama Radioheliograph, at
Nobeyama Solar Radio Observatory and the hard X-ray (HXR) data taken with {\it
Reuven Ramaty High Energy Solar Spectroscopic Imager} obviously showed
nonthermal sources that are located above the flare loops during the preflare
phase. We performed imaging spectroscopic analyses on the nonthermal emission
sources both in microwaves and in HXRs, and confirmed that electrons are
accelerated from several tens of keV to more than 1 MeV even in this phase. If
we assume the thin-target model for the HXR emission source, the derived
electron spectral indices ($\sim 4.7$) is the same value as that from
microwaves ($\sim 4.7$) within the observational uncertainties, which implies
that the distribution of the accelerated electrons follows a single power-law.
The number density of the microwave-emitting electrons is, however, larger than
that of the HXR-emitting electrons, unless we assume low ambient plasma density
of about $1.0 \times 10^9$ cm$^{-3}$ for the HXR-emitting region. If we adopt
the thick-target model for the HXR emission source, on the other hand, the
electron spectral index ($\sim 6.7$) is much different, while the gap of the
number density of the accelerated electrons is somewhat reduced.

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The categories of this paper are: nucl-th
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The categories of this paper are: alg-geom
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The categories of this paper are: eess
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The categories of this paper are: chao-dyn
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The categories of this paper are: nucl-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: econ
31
The categories of this paper are: ao-sci
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The categories of this paper are: hep-th
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The categories of this paper are: adap-org
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The categories of this paper are: chem-ph
1
The categories of this paper are: cs
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The categories of this paper are: q-fin
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The categories of this paper are: hep-ex
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The categories of this paper are: math-ph
5
The categories of this paper are: gr-qc