Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Sigmoid-to-Flux-Rope Transition Leading to A Loop-Like Coronal Mass
  Ejection   Sigmoids are one of the most important precursor structures for solar
eruptions. In this Letter, we study a sigmoid eruption on 2010 August 1 with
EUV data obtained by the Atmospheric Imaging Assembly (AIA) on board the Solar
Dynamic Observatory (SDO). In AIA 94 \AA\ (Fe XVIII; 6 MK), topological
reconfiguration due to tether-cutting reconnection is unambiguously observed
for the first time, i.e., two opposite J-shaped loops reconnect to form a
continuous S-shaped loop, whose central portion is dipped and aligned along the
magnetic polarity inversion line (PIL), and a compact loop crossing the PIL. A
causal relationship between photospheric flows and coronal tether-cutting
reconnections is evidenced by the detection of persistent converging flows
toward the PIL using line-of-sight magnetograms obtained by the Helioseismic
and Magnetic Imager (HMI) on board SDO. The S-shaped loop remains in
quasi-equilibrium in the lower corona for about 50 minutes, with the central
dipped portion rising slowly at ~10 km s-1. The speed then increases to ~60 km
s-1 about 10 minutes prior to the onset of a GOES-class C3.2 flare, as the
S-shaped loop speeds up its transformation into an arch-shaped loop, which
eventually leads to a loop-like coronal mass ejection (CME). The AIA
observations combined with H? filtergrams as well as hard X-ray (HXR) imaging
and spectroscopy are consistent with most flare loops being formed by
reconnection of the stretched legs of less-sheared J-shaped loops that
envelopes the rising flux rope, in agreement with the standard tether-cutting
scenario.

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The categories of this paper are: hep-th
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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: physics
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The categories of this paper are: dg-ga
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The categories of this paper are: q-bio
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The categories of this paper are: math
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The categories of this paper are: cs
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The categories of this paper are: hep-lat
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The categories of this paper are: patt-sol
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The categories of this paper are: adap-org
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The categories of this paper are: econ
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The categories of this paper are: acc-phys
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The categories of this paper are: nlin
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The categories of this paper are: solv-int
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The categories of this paper are: alg-geom