Magnetic%20Field%20Overlying%20Solar%20Eruptive%20Regions%20and%20Kink%20and%20Torus%20Instabilities

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Magnetic Field Overlying Solar Eruptive Regions
and Kink and Torus Instabilities

• Yang Liu
• Stanford University

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Motivation
Confined eruption of kink instability. (FE
hereafter)
Full eruption of kink instability. (KI hereafter)
Full eruption of torus instability. (TI hereafter)
TRACE 171 movie. Courtesy of Schrijver
EIT 195
TRACE 1600 A. Courtesy of L. Green
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Motivation
Full eruption of kink instability (KI)
Failed eruption of kink instability (FE)
Full eruption of torus instability (TI)
Q what causes these different types of eruptions?
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Motivation

• MHD simulations (FE vs KI)

Courtesy Kliem Torok
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Motivation

• MHD simulation (KI vs TI)

Fan Gibson (2007)
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Motivation
FE versus KI
KI versus TI
suggest gradient of the overlying field decides
eruptions
n(FE)ltn(KI)ltn(TI)
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Methodology

• Select erupted filaments in active regions
• Calculate background field using a potential
  field source surface model
• At each height, compute overlying field by
  averaging horizontal field along the magnetic
  neutral line on the photosphere
• Derive decay index.

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Sample

• We collect events from literature, and found
• 4 failed eruption (FE) cases (Green et al. 2007)
• 4 kink-instability (KI) full eruption cases
  (Green et al. 2007 Williams, et al. 2005)
• 2 torus-instability (TI) full eruption cases
  (Schrijver et al. 2008).

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Result
ID Type Flare Date, Time (dd/mm/yy) AR Flux (e22 Max) n B_t _at_ 42 Mm (Gauss)
1 FE X1.1 06/06/00 1330 9026 5.93 1.51 58.4
2 FE ------ 19/07/00 2330 9077 6.76 1.65 44.2
3 FE ------ 27/05/02 1805 9957 6.98 1.71 51.3
4 FE M1.0 02/05/03 0247 0345 6.71 1.62 99.3
5 KI C6.8 07/04/97 1350 8027 1.12 1.75 12.6
6 KI C1.3 12/05/97 0442 8038 0.88 1.88 12.3
7 KI M6.3 15/06/01 0952 9502 1.99 1.85 28.3
8 KI X2.5 10/11/04 0156 0696 4.65 2.25 35.9
9 TI M4.0 16/06/05 1910 0775 3.70 2.04 26.4
10 TI M3.7 27/07/05 0300 0792 4.56 1.74 33.0
Decay index shows a clearly dividing line between
failed eruptions and full eruptions, supportive
of MHD simulations.
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Result
Type Flux (e22 Max) n B_t (Gauss)
FE 6.600.33 1.620.05 63.318.0
KI 2.161.25 1.930.15 22.39.8
TI 4.130.43 1.890.15 29.73.3
KITI 2.811.48 1.910.15 24.78.2

• n(FE)ltn(KI) n(FE)ltn(TI) ? support MHD results
• n(KI)n(TI) ? not support MHD results
• B(FE)gtB(KI) B(FE)gtB(TI), due to probably,
• F(FE)gtF(KI) F(FE)gtF(TI)?large active regions?
• Large active regions usually produce more events
• Eruptions may be caused by other mechanisms
• Initial heights of filaments are higher.

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Conclusions

• MHD simulations suggest n(FE)ltn(KI)ltn(TI).
• This work indicates
• n(FE)ltn(KI) n(FE)ltn(TI) but
• n(KI)n(TI)
• Field strength at low altitude is much stronger
  for failed eruption than for full eruptions.