Onset of Coronal Mass Ejections Due to Loss of Confinement of Coronal Flux Ropes

Fan, Yuhong; Gibson, S. E.

doi:10.1086/521335

Cited by 294 publications

(272 citation statements)

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“…The transition from the quasi-static to dynamic evolution constitutes the catastrophe, and the corresponding model for solar eruptions are known as the catastrophe model (see Lin et al 2003 for more details). Alternative models to the catastrophe one for triggering eruptions include the sheared arcade model (Mikić et al 1988;Mikić and Linker 1994;Linker et al 2003;Amari et al 2005Amari et al , 2010), the breakout model (Antiochos et al 1999;Lynch et al 2010;Karpen et al 2012), the ideal MHD model on the basis of the kink and torus instability (Titov and Démoulin 1999;Török and Kliem 2005;Kliem and Török 2006;Fan and Gibson 2007;Karlický and Kliem 2010), the tether-cutting model (Moore et al 2001), and so on (see also Shibata and Magara 2011;Yang et al 2012;Schmieder et al 2013;Yan et al 2014).…”

Section: Introductionmentioning

confidence: 99%

Review on Current Sheets in CME Development: Theories and Observations

et al. 2015

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We introduce how the catastrophe model for solar eruptions predicted the formation and development of the long current sheet (CS) and how the observations were used to recognize the CS at the place where the CS is presumably located. Then, we discuss the direct measurement of the CS region thickness by studying the brightness distribution of the CS region at different wavelengths. The thickness ranges from 10 4 km to about 10 5 km at heights between 0.27 and 1.16 R from the solar surface. But the traditional theory indicates that the CS is as thin as the proton Larmor radius, which is of order tens of meters in the corona. We look into the huge difference in the thickness between observations and theoretical expectations. The possible impacts that affect measurements and results are studied, and physical causes leading to a thick CS region in which reconnection can still occur at a reasonably fast rate are analyzed. Studies in both theories and observations suggest that the difference between the true value and the apparent value of the CS thickness is not significant as long as the CS could be recognised in observations. We review observations that show complex structures and flows inside the CS region and present recent numerical modelling results on some aspects of these structures. Both observations and numerical experiments indicate that the downward reconnection outflows are usually slower than the upward ones in the same eruptive event. Numerical simulations show that the complex structure inside CS and its temporal behavior as a result of turbulence and the Petschek-type slow-mode shock could probably account for the thick CS and fast reconnection. But whether the CS itself is that thick still remains unknown since, for the time being, we cannot measure the electric current directly in that region. We also review the most recent laboratory experiments of reconnection driven by energetic laser beams, and discuss some important topics for future works.

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Section: Introductionmentioning

confidence: 99%

Review on Current Sheets in CME Development: Theories and Observations

et al. 2015

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“…Over the years, a wide variety of models have been put forward to explain the origin of CMEs, and a discussion of these can be seen in the reviews of Forbes et al (2006) and Chen (2011). While a variety of models exist, one of the leading models for explaining CMEs is the flux rope ejection model (Forbes & Isenberg 1991;Amari et al 2000;Fan & Gibson 2007). The flux rope ejection model may itself be split into two categories.…”

Section: Introductionmentioning

confidence: 99%

Magnetohydrodynamic simulations of the ejection of a magnetic flux rope

Pagano

Mackay

Poedts

2013

A&A

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Context. Coronal mass ejections (CME's) are one of the most violent phenomena found on the Sun. One model to explain their occurrence is the flux rope ejection model. In this model, magnetic flux ropes form slowly over time periods of days to weeks. They then lose equilibrium and are ejected from the solar corona over a few hours. The contrasting time scales of formation and ejection pose a serious problem for numerical simulations. Aims. We simulate the whole life span of a flux rope from slow formation to rapid ejection and investigate whether magnetic flux ropes formed from a continuous magnetic field distribution, during a quasi-static evolution, can erupt to produce a CME. Methods. To model the full life span of magnetic flux ropes we couple two models. The global non-linear force-free field (GNLFFF) evolution model is used to follow the quasi-static formation of a flux rope. The MHD code ARMVAC is used to simulate the production of a CME through the loss of equilibrium and ejection of this flux rope. Results. We show that the two distinct models may be successfully coupled and that the flux rope is ejected out of our simulation box, where the outer boundary is placed at 2.5 R . The plasma expelled during the flux rope ejection travels outward at a speed of 100 km s −1 , which is consistent with the observed speed of CMEs in the low corona. Conclusions. Our work shows that flux ropes formed in the GNLFFF can lead to the ejection of a mass loaded magnetic flux rope in full MHD simulations. Coupling the two distinct models opens up a new avenue of research to investigate phenomena where different phases of their evolution occur on drastically different time scales.

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“…"Current increase", for example via emergence of strongly-twisted flux ropes from below the surface (Leka et al 1996), could also result in eruption (e.g., Amari et al 2004). Another source for the onset of fast eruption is an "ideal MHD instability", for example driven by continued shearing of photospheric fields, where the fast eruption begins without pre-existing current sheets and reconnection (e.g., Kliem & Török 2006;Fan & Gibson 2007). Even in this case however, in most if not all events internal tether-cutting reconnection begins soon after the start of the fast eruption of the sheared core field and produces most of the event's particle acceleration and flare heating.…”

Section: Introductionmentioning

confidence: 99%

Evidence for magnetic flux cancelation leading to an ejective solar eruption observed byHinode,TRACE,STEREO, andSoHO/MDI

Sterling¹,

Chifor²,

Mason³

et al. 2010

A&A

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Aims. We study the onset of a solar eruption involving a filament ejection on 2007 May 20. Methods. We observe the filament in Hα images from Hinode/SOT and in EUV with TRACE and STEREO/SECCHI/EUVI. Hinode/XRT images are used to study the eruption in soft X-rays. From spectroscopic data taken with Hinode/EIS we obtain bulkflow velocities, line profiles, and plasma densities in the onset region. The magnetic field evolution was observed in SoHO/MDI magnetograms. Results. We observed a converging motion between two opposite polarity sunspots that form the primary magnetic polarity inversion line (PIL), along which resides filament material before eruption. Positive-flux magnetic elements, perhaps moving magnetic features (MMFs) flowing from the spot region, appear north of the spots, and the eruption onset occurs where these features cancel repeatedly in a negative-polarity region north of the sunspots. An ejection of material observed in Hα and EUV marks the start of the filament eruption (its "fast-rise"). The start of the ejection is accompanied by a sudden brightening across the PIL at the jet's base, observed in both broad-band images and in EIS. Small-scale transient brightenings covering a wide temperature range (Log T e = 4.8−6.3) are also observed in the onset region prior to eruption. The preflare transient brightenings are characterized by sudden, localized density enhancements (to above Log n e [cm −3 ] = 9.75, in Fe xiii) that appear along the PIL during a time when pre-flare brightenings were occurring. The measured densities in the eruption onset region outside the times of those enhancements decrease with temperature.Persistent downflows (red-shifts) and line-broadening (Fe xii) are present along the PIL.Conclusions. The array of observations is consistent with the pre-eruption sheared-core magnetic field being gradually destabilized by evolutionary tether-cutting flux cancelation that was driven by converging photospheric flows, and the main filament ejection being triggered by flux cancelation between the positive flux elements and the surrounding negative field. A definitive statement however on the eruption's ultimate cause would require comparison with simulations, or additional detailed observations of other eruptions occurring in similar magnetic circumstances.

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Onset of Coronal Mass Ejections Due to Loss of Confinement of Coronal Flux Ropes

Cited by 294 publications

References 28 publications

Review on Current Sheets in CME Development: Theories and Observations

Review on Current Sheets in CME Development: Theories and Observations

Magnetohydrodynamic simulations of the ejection of a magnetic flux rope

Evidence for magnetic flux cancelation leading to an ejective solar eruption observed byHinode,TRACE,STEREO, andSoHO/MDI

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