Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A study on the dynamic spectral indices for SEP events on 2000 July 14
  and 2005 January 20   We have studied the dynamic proton spectra for the two solar energetic
particle (SEP) events on 2000 July 14 (hereafter GLE59) and 2005 January 20
(hereafter GLE69). The source locations of GLE59 and GLE69 are N22W07 and
N12W58 respectively. Proton fluxes >30 MeV have been used to compute the
dynamic spectral indices of the two SEP events. The results show that spectral
indices of the two SEP events increased more swiftly at early times, suggesting
that the proton fluxes >30 MeV might be accelerated particularly by the
concurrent flares at early times for the two SEP events. For the GLE69 with
source location at N12W58, both flare site and shock nose are well connected
with the Earth at the earliest time. However, only the particles accelerated by
the shock driven by eastern flank of the CME can propagate along the
interplanetary magnetic field line to the Earth after the flare. For the GLE59
with source location at N22W07, only the particles accelerated by the shock
driven by western flank of the associated CME can reach the Earth after the
flare. Results show that there was slightly more than one hour during which the
proton spectra for GLE69 are softer than that for GLE59 after the flares,
suggesting that the shock driven by eastern flank of the CME associated with
GLE69 is weaker than the shock driven by the western flank of the CME
associated with GLE59. The results support that quasi-perpendicular shock has
stronger potential in accelerating particles than the quasi-parallel shock. The
results also suggest that only a small part of the shock driven by western
flank of the CME associated with the GLE59 is quasi-perpendicular.

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The categories of this paper are: nucl-ex
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The categories of this paper are: chem-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-th
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The categories of this paper are: chao-dyn
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The categories of this paper are: alg-geom
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The categories of this paper are: math-ph
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The categories of this paper are: stat
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The categories of this paper are: cond-mat
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The categories of this paper are: hep-lat
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The categories of this paper are: econ
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The categories of this paper are: solv-int
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The categories of this paper are: hep-th
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The categories of this paper are: hep-ex
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The categories of this paper are: patt-sol