Flux Rope Formation Preceding Coronal Mass Ejection Onset

Green, L. M.; Kliem, B.

doi:10.1088/0004-637x/700/2/l83

Cited by 124 publications

(92 citation statements)

References 34 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Phase one is a phase of increasing shear driven by the dispersal and cancellation of flux; in phase two there is an accumulation of a significant amount of flux that runs almost parallel to the PIL (axial flux) so that a remnant active region field that has not yet been involved in flux cancellation, takes on the appearance of two J's either side of the axial flux; phase three involves further flux cancellation that produces field lines that are twisted around the axial flux (which look S-shaped) and which contribute poloidal flux and define the presence of a flux rope (Green and Kliem, 2014, see Figure 15). In light of this, sigmoids formed in decaying active regions that contain continuous S-shaped structures that have an inverse crossing of the PIL by the middle, bracketed by two regular PIL crossings by the sigmoid elbows show support for the presence of a flux rope (Green and Kliem, 2009). Such an understanding of the magnetic configuration helps explain why sigmoidal active regions have such a high tendency to produce coronal mass ejections .…”

Section: The Build-up Of Magnetic Flux Ropes and Filamentsmentioning

confidence: 85%

“…If it is inversely directed along a section of the PIL, it suggests the presence of a 'bald patch' formed by a concave-up configuration produced by the field lines at the bottom of a flux rope if the rope reaches down to the photosphere (Athay et al, 1983;Lites, 2005;Canou et al, 2009). Another approach is to study continuous S-shaped (sigmoidal) sources of X-ray and EUV emission, which follow the magnetic field lines, and which exhibit an inverse crossing of the PIL in the centre of the sigmoid -indicating that they are created by helical magnetic configurations (Green and Kliem, 2009). Work that studies the formation of sigmoidal structures in decaying active regions indicates that the coronal field does indeed evolve as described by van Ballegooijen and Martens (1989).…”

Section: The Build-up Of Magnetic Flux Ropes and Filamentsmentioning

confidence: 99%

See 1 more Smart Citation

Evolution of Active Regions

Driel-Gesztelyi

Green

2015

Living Rev. Sol. Phys.

252

131

View full text Add to dashboard Cite

The evolution of active regions (AR) from their emergence through their long decay process is of fundamental importance in solar physics. Since large-scale flux is generated by the deepseated dynamo, the observed characteristics of flux emergence and that of the subsequent decay provide vital clues as well as boundary conditions for dynamo models. Throughout their evolution, ARs are centres of magnetic activity, with the level and type of activity phenomena being dependent on the evolutionary stage of the AR. As new flux emerges into a pre-existing magnetic environment, its evolution leads to re-configuration of small-and large-scale magnetic connectivities. The decay process of ARs spreads the once-concentrated magnetic flux over an ever-increasing area. Though most of the flux disappears through small-scale cancellation processes, it is the remnant of large-scale AR fields that is able to reverse the polarity of the poles and build up new polar fields. In this Living Review the emphasis is put on what we have learned from observations, which is put in the context of modelling and simulation efforts when interpreting them. For another, modelling-focused Living Review on the sub-surface evolution and emergence of magnetic flux see Fan (2009). In this first version we focus on the evolution of dominantly bipolar ARs. Article RevisionsLiving Reviews supports two ways of keeping its articles up-to-date:Fast-track revision. A fast-track revision provides the author with the opportunity to add short notices of current research results, trends and developments, or important publications to the article. A fast-track revision is refereed by the responsible subject editor. If an article has undergone a fast-track revision, a summary of changes will be listed here.Major update. A major update will include substantial changes and additions and is subject to full external refereeing. It is published with a new publication number.For detailed documentation of an article's evolution, please refer to the history document of the article's online version at http://dx

show abstract

Section: The Build-up Of Magnetic Flux Ropes and Filamentsmentioning

confidence: 85%

Section: The Build-up Of Magnetic Flux Ropes and Filamentsmentioning

confidence: 99%

Evolution of Active Regions

Driel-Gesztelyi

Green

2015

Living Rev. Sol. Phys.

252

131

View full text Add to dashboard Cite

show abstract

“…Such features are referred to as bald patches, BP (Seehafer 1986;Titov et al 1993;Bungey et al 1996;. They have been suggested as sites where partial eruptions originate and where sigmoidal coronal sources form (Gibson et al 2004;Green & Kliem 2009). …”

Section: Test Equilibriamentioning

confidence: 99%

Testing magnetofrictional extrapolation with the Titov-Démoulin model of solar active regions

Valori¹,

Kliem

Török³

et al. 2010

A&A

Self Cite

View full text Add to dashboard Cite

We examine the nonlinear magnetofrictional extrapolation scheme using the solar active region model by Titov and Démoulin as test field. This model consists of an arched, line-tied current channel held in force-free equilibrium by the potential field of a bipolar flux distribution in the bottom boundary. A modified version with a parabolic current density profile is employed here. We find that the equilibrium is reconstructed with very high accuracy in a representative range of parameter space, using only the vector field in the bottom boundary as input. Structural features formed in the interface between the flux rope and the surrounding arcade -"hyperbolic flux tube" and "bald patch separatrix surface" -are reliably reproduced, as are the flux rope twist and the energy and helicity of the configuration. This demonstrates that force-free fields containing these basic structural elements of solar active regions can be obtained by extrapolation. The influence of the chosen initial condition on the accuracy of reconstruction is also addressed, confirming that the initial field that best matches the external potential field of the model quite naturally leads to the best reconstruction. Extrapolating the magnetogram of a Titov-Démoulin equilibrium in the unstable range of parameter space yields a sequence of two opposing evolutionary phases, which clearly indicate the unstable nature of the configuration: a partial buildup of the flux rope with rising free energy is followed by destruction of the rope, losing most of the free energy.

show abstract

“…Sigmoids are continuous S-shaped (or inverse-S-shaped) plasma structures that appear strongly in X-ray bands, but also at hot extreme-ultraviolet (EUV) wavelengths. Their shape is representative of weakly twisted magnetic field bundles, and they may be an indicator of flux rope presence (Rust and Kumar, 1996;Green and Kliem, 2009). Plasmoids are generally features seen in events near the solar limb.…”

Section: Introductionmentioning

confidence: 99%

On-Disc Observations of Flux Rope Formation Prior to Its Eruption

et al. 2017

Self Cite

View full text Add to dashboard Cite

Coronal mass ejections (CMEs) are one of the primary manifestations of solar activity and can drive severe space weather effects. Therefore, it is vital to work towards being able to predict their occurrence. However, many aspects of CME formation and eruption remain unclear, including whether magnetic flux ropes are present before the onset of eruption and the key mechanisms that cause CMEs to occur. In this work, the pre-eruptive coronal configuration of an active region that produced an interplanetary CME with a clear magnetic flux rope structure at 1 AU is studied. A forward-S sigmoid appears in extremeultraviolet (EUV) data two hours before the onset of the eruption (SOL2012-06-14), which is interpreted as a signature of a right-handed flux rope that formed prior to the eruption. Flare ribbons and EUV dimmings are used to infer the locations of the flux rope footpoints. These locations, together with observations of the global magnetic flux distribution, indicate that an interaction between newly emerged magnetic flux and pre-existing sunspot field in the days prior to the eruption may have enabled the coronal flux rope to form via tethercutting-like reconnection. Composition analysis suggests that the flux rope had a coronal plasma composition, supporting our interpretation that the flux rope formed via magnetic reconnection in the corona. Once formed, the flux rope remained stable for two hours before erupting as a CME. Electronic supplementary material The online version of this article

show abstract

Flux Rope Formation Preceding Coronal Mass Ejection Onset

Cited by 124 publications

References 34 publications

Evolution of Active Regions

Evolution of Active Regions

Testing magnetofrictional extrapolation with the Titov-Démoulin model of solar active regions

On-Disc Observations of Flux Rope Formation Prior to Its Eruption

Contact Info

Product

Resources

About