Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Narrowband Gyrosynchrotron Bursts: Probing Electron Acceleration in
  Solar Flares   Recently, in a few case studies we demonstrated that gyrosynchrotron
microwave emission can be detected directly from the acceleration region when
the trapped electron component is insignificant. For the statistical study
reported here, we have identified events with steep (narrowband) microwave
spectra that do not show a significant trapped component and at the same time
show evidence of source uniformity, which simplifies the data analysis greatly.
Initially, we identified a subset of more than 20 radio bursts with such narrow
spectra, having low- and high-frequency spectral indices larger than 3 in
absolute value. A steep low-frequency spectrum implies that the emission is
nonthermal (for optically-thick thermal emission, the spectral index cannot be
steeper than 2), and the source is reasonably dense and uniform. A steep
high-frequency spectrum implies that no significant electron trapping occurs;
otherwise a progressive spectral flattening would be observed. Roughly half of
these radio bursts have RHESSI data, which allows for detailed, joint
diagnostics of the source parameters and evolution. Based on an analysis of
radio-to-X-ray spatial relationships, timing, and spectral fits, we conclude
that the microwave emission in these narrowband bursts originates directly from
the acceleration regions, which have relatively strong magnetic field, high
density, and low temperature. In contrast, the thermal X-ray emission comes
from a distinct loop with smaller magnetic field, lower density, but higher
temperature. Therefore, these flares occurred likely due to interaction between
two (or more) magnetic loops.

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The categories of this paper are: cs
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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: bayes-an
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The categories of this paper are: eess
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The categories of this paper are: hep-th
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The categories of this paper are: q-fin
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The categories of this paper are: ao-sci
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The categories of this paper are: adap-org
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The categories of this paper are: mtrl-th
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The categories of this paper are: patt-sol
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The categories of this paper are: physics
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The categories of this paper are: econ
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The categories of this paper are: funct-an
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The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom