Sigmoid-to-flux-rope transition leading to a loop-like coronal mass ejection

Rui Liu, Chang Liu, Shuo Wang, Na Deng, Haimin Wang

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120 Scopus citations


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 Å (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 tethercutting 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 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 looplike coronal mass ejection. The AIA observations combined with Hα filtergrams as well as hard X-ray imaging and spectroscopy are consistent with most flare loops being formed by reconnection of the stretched legs of lesssheared J-shaped loops that envelopes the rising flux rope, in agreement with the standard tether-cutting scenario.

Original languageEnglish (US)
Pages (from-to)L84-L90
JournalAstrophysical Journal Letters
Issue number1 PART 2
StatePublished - Dec 10 2010

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Sun: coronal mass ejections (CMEs)
  • Sun: filaments, prominences
  • Sun: flares


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