Formation of current sheets and sigmoidal structure by the kink instability of a magnetic loop

By B. Kliem, Viacheslav S. Titov, Tibor Török. 2003

168 citations recorded by the source corpus.

We study dynamical consequences of the kink instability of a twisted coronal flux rope, using the force-free coronal loop model by Titov & Demoulin (1999) as the initial condition in ideal-MHD simulations. When a critical value of the twist is exceeded, the long-wavelength (m=1) kink mode develops. Analogous to the well-known cylindrical approximation, a helical current sheet is then formed at the interface with the surrounding medium. In contrast to the cylindrical case, upward-kinking loops form a second, vertical current sheet below the loop apex at the position of the hyperbolic flux tube (generalized X line) in the model. The current density is steepened in both sheets and eventually exceeds the current density in the loop (although the kink perturbation starts to saturate in our simulations without leading to a global eruption). The projection of the field lines that pass through the vertical current sheet shows an S shape whose sense agrees with the typical sense of transient sigmoidal ( forward or reverse S-shaped) structures that brighten in soft X rays prior to coronal eruptions. The upward-kinked loop has the opposite S shape, leading to the conclusion that such sigmoids do not generally show the erupting loops themselves but indicate the formation of the vertical current sheet below them that is the central element of the standard flare model.

Subfields: Astronomy and Astrophysics, Molecular Biology

View Paper: https://www.semanticscholar.org/paper/e1b7e9e4618b49cd8871c5e13e2b157d62c33211

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Citations in the corpus

Three-dimensional magnetic reconnection regimes: a review (2011, background): “Furthermore, numerical modelling of the loss of stability and subsequent eruption of flux ropes has implicated reconnection in a QSL beneath the flux rope (Titov and Démoulin, 1999; Kliem et al., 2004; Titov et al., 2008).”
Generalized Squashing Factors for Covariant Description of Magnetic Connectivity in the Solar Corona (2007, background): “Figure 5a suggests that the sigmoids in such configurations are simply pinching HFTs illuminated by a hot plasma material which appears there due to the reconnection process in the above-mentioned vertical current sheet.”
Coronal prominence structure and dynamics: A magnetic flux rope interpretation (2006, methodology): “These reconnected field lines, rather than the current sheet itself, are arguably the most appropriate proxies for the soft X-ray sigmoid [Kliem et al., 2004].”
Confined and Ejective Eruptions of Kink-unstable Flux Ropes (2005, background): “Further essential features of solar eruptions could be reproduced in the simulations as, for example, the formation of transient soft X-ray sigmoids (Kliem et al. 2004, hereafter Paper II).”
Tracking Vector Magnetograms with the Magnetic Induction Equation (2008, background): “…flux cancellation of the overlying coronal field (Linker et al. 2001), flux injection (Chen 1989, 1996), the kink instability of filaments (Rust & Kumar 1996; Török et al. 2004; Kliem et al. 2004), and photospheric footpoint shearing (Amari et al. 2000, 2003a, 2003b; Schrijver et al. 2005).”
The Calm before the Storm: The Link between Quiescent Cavities and Coronal Mass Ejections (2006, background): “…Rust 1994; Rust & Kumar 1994; Lites & Low 1997; Gibson & Low 1998; Aulanier & Démoulin 1998), X-ray sigmoids (Rust & Kumar 1994; Titov & Démoulin 1999; Low & Berger 2003; Fan & Gibson 2003, 2004; Kliem et al. 2004; Gibson et al. 2004), and three-part CMEs and magnetic clouds, as referenced above.”
Interplanetary flux rope ejected from an X-ray bright point. The smallest magnetic cloud source-region ever observed (2005, result): “The results of these topological studies are supported by the recent numerical simulations of Fan & Gibson (2003), Gibson et al. (2004) and Kliem et al. (2004).”
Coronal Mass Ejections as Loss of Confinement of Kinked Magnetic Flux Ropes (2005, background): “Fan & Gibson (2003, 2004), Kliem et al. (2004), and Gibson et al. (2004) have discussed in detail how the current sheet forms and its close relation to the baldpatch separatrix surface that separates the twisted field lines that graze the photosphere and the neighboring anchored field lines (Titov…”
Ideal kink instability of a magnetic loop equilibrium (2003, background): “The implications of the helical kinking and current sheet formation for the int rpretation of sigmoidal structures in the solar corona have been discussed in Kliem et al. (2003).”
The Physical Processes of CME/ICME Evolution (2017, background): “…1991), the structure starts to accelerate, driven by some form of ideal MHD instabilities such as the kink or torus modes (e.g., and references therein Török and Kliem 2003, 2005; Kliem et al. 2004; Kliem and Török 2006; Démoulin and Aulanier 2010; Olmedo and Zhang 2010; Török et al. 2010).”
The Partial Expulsion of a Magnetic Flux Rope (2006, background): “…a pre-CME flux rope (Wolfson et al. 1987; Low & Hundhausen 1995; Linker et al. 2003; Gibson et al. 2006), as are transient sigmoid brightenings (Rust & Kumar 1996; Fan & Gibson 2003, 2004; Kliem et al. 2004) and their transition to cusped postflare loops (Amari et al. 2003b; To¨rök & Kliem 2005).”