Helical kink instability in the confined solar eruption on 2002 May 27

Hassanin, Alshaimaa; Kliem, B.; Seehafer, N.

doi:10.1002/asna.201612446

Cited by 5 publications

(2 citation statements)

References 30 publications

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“…In particular, there are many indications that the kink instability of coronal magnetic flux ropes can cause coronal mass ejections (CMEs) and solar flares (see, e.g., Sakurai 1976;Rust & Kumar 1996;Williams et al 2005;Forbes 2010; Myers et al 2015;Liu 2020). However, the issue of magnetohydrodynamic (MHD) stability conditions of flux ropes is not fully resolved (e.g., Dungey & Loughhead 1954;Priest 1984;Bennett et al 1999;Hassanin et al 2016;Tsap et al 2020). This is mostly explained by the strong dependence of MHD stability on the magnetic field configuration not only inside (e.g., Hood & Priest 1979;Mikic et al 1990;Bennett et al 1999;Baty 2001) but also outside (e.g., Hood & Priest 1980;) a flux rope.…”

Section: Introductionmentioning

confidence: 99%

On the Kink Instability of Twisted Coronal Loops: Nonneutralized Electric Current

Tsap

Stepanov

Kopylova

2022

ApJ

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Based on linear magnetohydrodynamic equations and an energy principle we analyze the ideal kink instability of a twisted force-free coronal loop (flux rope) surrounded by an outer potential magnetic field by using the sharp-boundary approximation at the surface. Unlike Tsap et al., a magnetic flux rope with nonneutralized (uncompensated) electric current is considered. We have shown that the twist angle of magnetic field lines is closely related to coronal mass ejections and solar flares. The kink instability condition does not depend on the radial profile of the magnetic field inside a flux rope in the long-wavelength limit but depends strongly on the reverse electric currents at the surface. The total critical twist angle of magnetic field lines, which determines the kink instability threshold, can be much greater than π radians due to reverse azimuthal surface current. This agrees with observations and illustrates the importance of the role of reverse currents for stabilization of a flux rope. Additional arguments in favor of the energy release models based on the uncompensated electric currents are presented.

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Section: Introductionmentioning

confidence: 99%

On the Kink Instability of Twisted Coronal Loops: Nonneutralized Electric Current

Tsap

Stepanov

Kopylova

2022

ApJ

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“…Kink instability is a subject of special interest since there is much evidence that this instability can be responsible for flare energy release and coronal mass ejections (see, e.g., Sakurai 1976;Török & Kliem 2005;Myers et al 2015;Chen 2017). However, the question about the stability conditions of flux ropes is not fully resolved yet (see, e.g., Priest 1984;Hassanin et al 2016).…”

Section: Introductionmentioning

confidence: 99%

On the Stabilization of a Twisted Magnetic Flux Tube

Tsap

Fedun

Cheremnykh

et al. 2020

ApJ

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The linear magnetohydrodynamic stability of a shielding magnetic flux rope with a surface current under coronal solar conditions is analyzed in the framework of an energy principle. The equation describing the potential energy change induced by disturbances of the equilibrium was derived. It has been shown that the surface reverse current shielding the azimuthal component of the magnetic field lines outside a flux rope stabilizes the development of kink-and flute-type instabilities in the long-wavelength limit independently of the cross-sectional radial profile of current density. Kink modes are the most unstable ones as their generation requires less energy than other modes. Based on the obtained dispersion relation for kink oscillations, we proposed a new expression for the determination of magnetic field components of the twisted loop.

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Helicity shedding by flux rope ejection

Kliem

Seehafer

2022

A&A

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Context. We quantitatively address the conjecture that magnetic helicity must be shed from the Sun by eruptions launching coronal mass ejections in order to limit its accumulation in each hemisphere. Aims. By varying the ratio of guide and strapping field and the flux rope twist in a parametric simulation study of flux rope ejection from approximately marginally stable force-free equilibria, different ratios of self- and mutual helicity are set and the onset of the torus or helical kink instability is obtained. Methods. The helicity shed is found to vary over a broad range from a minor to a major part of the initial helicity, with self helicity being largely or completely shed and mutual helicity, which makes up the larger part of the initial helicity, being shed only partly. Torus-unstable configurations with subcritical twist and without a guide field shed up to about two-thirds of the initial helicity, while a highly twisted, kink-unstable configuration sheds only about one-quarter. The parametric study also yields stable force-free flux rope equilibria up to a total flux-normalized helicity of 0.25, with a ratio of self- to total helicity of 0.32 and a ratio of flux rope to external poloidal flux of 0.94. Results. These results numerically demonstrate the conjecture of helicity shedding by coronal mass ejections and provide a first account of its parametric dependence. Both self- and mutual helicity are shed significantly; this reduces the total initial helicity by a fraction of ∼0.4 − 0.65 for typical source region parameters.

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Helical kink instability in the confined solar eruption on 2002 May 27

Cited by 5 publications

References 30 publications

On the Kink Instability of Twisted Coronal Loops: Nonneutralized Electric Current

On the Kink Instability of Twisted Coronal Loops: Nonneutralized Electric Current

On the Stabilization of a Twisted Magnetic Flux Tube

Helicity shedding by flux rope ejection

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