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Romano, P.; Contarino, L.; Zuccarello, F.

doi:10.1023/a:1024257603143

Cited by 53 publications

(40 citation statements)

References 10 publications

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“…The height ranges from 42 Mm to 105 Mm. We choose 42 Mm for the starting height, the average of the initial heights from four events (events 2, 3, 9 and 10) for which the initial heights were obtained from observation (Schrijver et al 2008;Ji et al 2003;Romano et al 2003). The strength and height are in logarithm.…”

Section: Events and Analysismentioning

confidence: 99%

Magnetic Field Overlying Solar Eruption Regions and Kink and Torus Instabilities

Liu

2008

ApJ

150

154

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Using a Potential Field Source Surface model (PFSS), we study magnetic field overlying erupted filaments in solar active regions. The filaments studied here were reported to experience a kink instability or a torus instability. The torus instability leads to a full eruption, while the kink instability leads to a full eruption or a failed eruption. It is found that for full eruption the field decreases with height more quickly than that for failed eruption. A dividing line between full eruption and failed eruption is also found to be likely connected with the decay index n of the horizontal potential field due to sources external of the filament ( n = −d log(B ex )/d log(h), where h is height): the decay index of failed eruption tends to be smaller than that of full eruption. The difference of the decay indexes between full eruption and failed eruption is statistically significant. These are supportive of previous theoretical and numerical simulation results. Another significant difference is the field strength at low altitude: for failed eruption, the field strength is about a factor of 3 stronger than that for the full eruption. It suggests that the field strength at low altitude may be another factor in deciding whether or not a full eruption can take place. On the other hand, the decay index for the torus-instability full eruption events exhibits no trend to exceed the decay index for the kink-instability full eruption events on average, different from a suggestion derived from some MHD simulations. We discuss possible reasons that may cause this discrepancy.

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Section: Events and Analysismentioning

confidence: 99%

Magnetic Field Overlying Solar Eruption Regions and Kink and Torus Instabilities

Liu

2008

ApJ

150

154

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“…We conclude that the senses of twist and writhe were both positive in this event. Romano et al (2003) also analyzed this filament eruption. They also concluded that the filament was kinking, based on their measured decrease in the ratio between the pitch of the magnetic field lines and the filament width.…”

Section: Writhing Filaments In Trace Moviesmentioning

confidence: 99%

Observational Evidence of the Kink Instability in Solar Filament Eruptions and Sigmoids

Rust

Labonte

2005

ApJ

114

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Two lines of observational evidence are used to infer that the MHD helical kink instability is associated with solar eruptions. The senses of twist and writhe are determined in images of seven erupting filaments obtained at 10830, 1600, 195, and 171 . In every case the sense of twist is the same as the sense of writhe, as required A for a kink. From images in the soft X-ray and EUV spectrum, measurements of the height/width ratio of 623 sigmoids show a mean value of 5.47, which is the ratio expected for kinked flux ropes.

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“…First of all, eruptive structures with a clear writhing feature are relatively rare, which raises a question as to how often the kink instability triggers eruptions. Second, twisted, helical patterns are often exposed only during eruptions (e.g., Vrsnak et al 1991Vrsnak et al , 1993Romano et al 2003;Gary & Moore 2004;Srivastava et al 2010;Kumar et al 2012). It is hence difficult to determine whether the twist is accumulated prior to the eruption or built up in the course of the eruption through reconnection in the vertical current sheet under the rope (Lin et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Structure, Stability, and Evolution of Magnetic Flux Ropes From the Perspective of Magnetic Twist

Kliem

Titov

et al. 2016

ApJ

289

314

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We investigate the evolution of NOAA Active Region 11817 during 2013 August 10-12, when it developed a complex field configuration and produced four confined, followed by two eruptive, flares. These C-and-above flares are all associated with a magnetic flux rope (MFR) located along the major polarity inversion line, where shearing and converging photospheric flows are present. Aided by the nonlinear force-free field modeling, we identify the MFR through mapping magnetic connectivities and computing the twist number T w for each individual field line. The MFR is moderately twisted (|T w | < 2) and has a well-defined boundary of high squashing factor Q. We found that the field line with the extremum |T w | is a reliable proxy of the rope axis, and that the MFR's peak |T w | temporarily increases within half an hour before each flare while it decreases after the flare peak for both confined and eruptive flares. This pre-flare increase 9 Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, 37077 Göttingen, Germany -2 -in |T w | has little effect on the active region's free magnetic energy or any other parameters derived for the whole region, due to its moderate amount and the MFR's relatively small volume, while its decrease after flares is clearly associated with the stepwise decrease in the whole region's free magnetic energy due to the flare. We suggest that T w may serve as a useful parameter in forewarning the onset of eruption, and therefore, the consequent space weather effects. The helical kink instability is identified as the prime candidate onset mechanism for the considered flares.

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Cited by 53 publications

References 10 publications

Magnetic Field Overlying Solar Eruption Regions and Kink and Torus Instabilities

Magnetic Field Overlying Solar Eruption Regions and Kink and Torus Instabilities

Observational Evidence of the Kink Instability in Solar Filament Eruptions and Sigmoids

Structure, Stability, and Evolution of Magnetic Flux Ropes From the Perspective of Magnetic Twist

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