The Emergence of a Twisted Flux Tube Into the Solar Atmosphere: Sunspot Rotations and the Formation of a Coronal Flux Rope

Fan, Yuhong

doi:10.1088/0004-637x/697/2/1529

Cited by 165 publications

(220 citation statements)

References 26 publications

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“…Gibson & Fan 2006;Archontis et al 2009). The formation of a coronal flux rope with a sigmoidal shape has also been reported in the simulations by Fan (2009). The rotational motions of the two opposite polarities of an emerged flux tube are found to twist up the inner field lines such as they change their orientation into an inverse configuration.…”

Section: Introductionsupporting

confidence: 64%

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Magnetic flux emergence: a precursor of solar plasma expulsion

Archontis

Hood

2012

A&A

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Aims. We model the emergence of magnetized plasma from the top of the convection zone to the lower corona. We investigate the eruption of coronal flux ropes above emerging flux regions. Methods. We performed three-dimensional numerical experiments in which the time-dependent and resistive equations of MHD are solved self-consistently, using the Lare3D code. Results. A subphotospheric magnetic flux tube rises from the convectively unstable layer into the solar surface, followed by the formation and eruption of a new flux rope into the corona. Firstly, we examined the case where the corona is field-free. The expansion of the emerging field forms an envelope sheath that surrounds the newly formed flux rope. The erupting ropes are confined by the envelope field. The eruptions are driven by the gradient of the gas pressure and the tension of fieldlines that reconnect within the emerging flux region. The amount of the initial twist of the emerging field and the dense plasma that is lifted up, determine the heighttime profile of the erupting ropes. Secondly, we examined the case of emergence into a pre-existing magnetic field in the upper solar atmosphere. A variety of different ambient field configurations was used in the experiments. External reconnection between the emerging and the pre-existing field may result in the removal of sufficient flux from the interacting fields and the full ejection of the flux ropes. Conclusions. The results indicate that the relative contact angle of the interacting flux systems and their field strengths are crucial parameters that ultimately affect the evolution of the eruption of the rope into the higher solar atmosphere. One important result is that for any contact angle that favors reconnection, ejective eruptions occur earlier when the ambient field is relatively strong. In many cases, the erupting plasma adopts an S-like configuration. The sigmoidal structure accelerates during the fast eruption of the rope. The acceleration is enhanced by the external and internal reconnection of fieldlines during the rising motion of the rope. A key result is that in the reconnection-favored cases, the flux ropes experience ejective eruptions when the envelope flux is reduced (owing to removal by external reconnection) below that of the erupting flux rope. If the envelope flux stays higher than the erupting flux, the magnetic flux rope remains confined by the envelope field.

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Section: Introductionsupporting

confidence: 64%

“…Magara & Longcope 2001;Manchester et al 2004;Archontis & Török 2008;Fan 2009) have shown that a new flux rope, which is formed at the upper photosphere, is able to erupt into the corona. Figure 2 (left) shows the cross section of such a flux rope in one of our experiments without a pre-existing ambient coronal field.…”

Section: Emergence and Coronal Eruptionsmentioning

confidence: 99%

Magnetic flux emergence: a precursor of solar plasma expulsion

Archontis

Hood

2012

A&A

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“…Theoretical simulations confirm that scenario (e.g. Fan 2009). But still is only a few direct observations of the formation of a flux rope (e.g.…”

Section: Introductionsupporting

confidence: 64%

Plasma diagnostics in two kinematic classes of CMEs observed by the Atmospheric Imaging Assembly onboard the Solar Dynamic Observatory

et al. 2016

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In order to study the dynamics and thermal properties of two kinematic classes of coronal mass ejections (CMEs) we analyzed two well-observed events in the early stage of their propagation, using multiwavelength observations from the Atmospheric Imaging Assembly (AIA) of the Solar Dynamic Observatory (SDO). For deriving differential emission measure (DEM) profiles and DEM maps of the basic structures of CMEs, we used two methods: the regularized inversion and the iterative forward-fitting approach. For the CME associated with a M2.0 class flare (CME-FL), we identified a hot, moving, blob-like feature which seems to be a candidate for a CME flux rope. Furthermore, an expanding system of loop and coronal dimming was clearly seen in AIA images. For the CME related to an eruptive prominence (CME-EP), we observed an eruptive plasmoid and a failed-eruption of cold plasma. However, we also recognized warm and hot moving signatures that revealed a multi-temperature nature of the eruptive prominence. Our main results are as follows: (a) An analysis of the examples of the two different kinematic classes of CMEs shows that despite the slight variations in the values of speeds and accelerations (CME-FL: v ≈ 174 km s −1 , a ≈ 350 m s −2 ; CME-EP: v ≈ 135 km s −1 , a ≈ 160 m s −2 ) they present the same kinematic behavior; (b) in the field of view of the LASCO coronagraphs these two events have the similar, positive accelerations; (c) for both events we observed an impulsive acceleration phase (IAP); (d) the expanding structures seen in 171 Å, 193 Å, 211 Å in both events move faster than the hotter blobs; (e) the plasmoid core for the CME-FL is hot (8.0-15.8 MK); (f) the expanding blob and the hot structure in the prominence region for the CME-EP event have the similar temperature range (0.8-2.5 MK).

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“…The rise of twisted magnetic fields has been studied by various authors through both observations (Lites et al 1995(Lites et al , 2010Leka et al 1996) and three-dimensional (3D) numerical simulations (e.g., Fan 2001; Archontis et al 2004;Magara 2004;Martínez-Sykora et al 2008;Fan 2009;Yelles Chaouche et al 2009). Such an emerging helical flux rope scenario, combined with the presence of granular flows, is supposedly the main process of formation and maintenance of the AR filament studied by Okamoto et al (2008Okamoto et al ( , 2009.…”

Section: Introductionmentioning

confidence: 99%

An active region filament studied simultaneously in the chromosphere and photosphere

Kuckein

Pillet

Centeno

2012

A&A

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Aims. A thorough multiwavelength, multiheight study of the vector magnetic field in a compact active region filament (NOAA 10781) on 2005 July 3 and 5 is presented. We suggest an evolutionary scenario for this filament. Methods. Two different inversion codes were used to analyze the full Stokes vectors acquired with the Tenerife Infrared Polarimeter (TIP-II) in a spectral range that comprises the chromospheric He i 10 830 Å multiplet and the photospheric Si i 10 827 Å line. In addition, we used SOHO/MDI magnetograms, as well as BBSO and TRACE images, to study the evolution of the filament and its active region (AR). High-resolution images of the Dutch Open Telescope were also used.Results. An active region filament (formed before our observing run) was detected in the chromospheric helium absorption images on July 3. The chromospheric vector magnetic field in this portion of the filament was strongly sheared (parallel to the filament axis), whereas the photospheric field lines underneath had an inverse polarity configuration. From July 3 to July 5, an opening and closing of the polarities on either side of the polarity inversion line (PIL) was recorded, resembling the recently discovered process of the sliding door effect seen by Hinode. This is confirmed with both TIP-II and SOHO/MDI data. During this time, a newly created region that contained pores and orphan penumbrae at the PIL was observed. On July 5, a normal polarity configuration was inferred from the chromospheric spectra, while strongly sheared field lines aligned with the PIL were found in the photosphere. In this same data set, the spine of the filament is also observed in a different portion of the field of view and is clearly mapped by the silicon line core. Conclusions. The inferred vector magnetic fields of the filament suggest a flux rope topology. Furthermore, the observations indicate that the filament is divided in two parts, one which lies in the chromosphere and another one that stays trapped in the photosphere. Therefore, only the top of the helical structure is seen by the helium lines. The pores and orphan penumbrae at the PIL appear to be the photospheric counterpart of the extremely low-lying filament. We suggest that orphan penumbrae are formed in very narrow PILs of compact ARs and are the photospheric manifestation of flux ropes in the photosphere.

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The Emergence of a Twisted Flux Tube Into the Solar Atmosphere: Sunspot Rotations and the Formation of a Coronal Flux Rope

Cited by 165 publications

References 26 publications

Magnetic flux emergence: a precursor of solar plasma expulsion

Magnetic flux emergence: a precursor of solar plasma expulsion

Plasma diagnostics in two kinematic classes of CMEs observed by the Atmospheric Imaging Assembly onboard the Solar Dynamic Observatory

An active region filament studied simultaneously in the chromosphere and photosphere

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