What is the role of the kink instability

What is the role of the kink instability in solar coronal eruptions? 太陽雑誌会速報 2003. 10. 06 Takako T. Ishii R. J. Leamon 1, R. C. Canfield 1, Z. Blehm 1 & A. A. Pevtsov 2 1 Dept. of Physics, Montana State Univ. 2 National Solar Observatory / Sacrament Peak Ap. J Letter, 596 (2003 Oct. 20) , rapid release Received: 2002 Dec. 11 Accepted: 2003 Sep. 04 Published: 2003 Sep. 29 Topics: Sigmoids, Twists, Eruptions

Sigmoid → Arcade, Eruption Kink instability L Force free field; g Pevtsov et al. 1997 L: separation between endpoints of a loop g: shear angle at which the central line crosses the line joining its endpoints ⇒ SXT images: 191 sigmoids (1991 Oct. ～ 2000 Oct. ) T: total twist ⇒ Mees Solar Observaotiry vector magnetograms → abest (1991 Oct. ～ 1998 Dec. ) Pevtsov et al. 1995, Longcope et al. 1998

Distributions of sing Measured Corrected for projection effect Average: 32 deg. 30 deg. 90 deg.

Distributions of L Measured Corrected for projection effect Average: 160 Mm 100, 000 km 400, 000 km

Number of eruptions per active regions (scaled per solar disk transit) No relation between sing and eruption Linear fit 1 s Not all sigmoids erupt

Distributions of total coronal twist T (25 flare-associated eruptive events) Broad distribution Many eruptions: T < 0. 5 p T > Tc= 2 p (unstable to the MHD kink mode) hour Long duration events hour