Active-Region Twist Derived from Magnetic Tongues and Linear Force-Free Extrapolations

Poisson, Mariano; Fuentes, M. C. López; Mandrini, C. H.; Démoulin, P.

doi:10.1007/s11207-015-0804-y

Cited by 13 publications

(15 citation statements)

References 35 publications

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“…During the latter phases of the emergence (Figures 10c,d), the primary polarities elongate, reminiscent of the behavior of the so-called 'magnetic tongues' (e.g., Luoni et al 2011;Poisson et al 2015Poisson et al , 2016, which originate from the azimuthal magnetic field component of the emerging flux rope. The horizontal magnetic field becomes strongly sheared along the polarity inversion lines separating the primary and secondary polarities (Figure 10d,e), since this field is created by short field lines encircling each leg of the flux rope.…”

Section: Photospheric Evolutionmentioning

confidence: 94%

The Role of Twist in Kinked Flux Rope Emergence and Delta-spot Formation

Knizhnik

Linton

DeVore

2018

ApJ

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It has been observationally well established that the magnetic configurations most favorable for producing energetic flaring events reside in δ-spots, a class of sunspots defined as having opposite polarity umbrae sharing a common penumbra. They are frequently characterized by extreme compactness, strong rotation and anti-Hale orientation. Numerous studies have shown that nearly all of the largest solar flares originate in δ-spots, making the understanding of these structures a fundamental step in predicting space weather. Despite their important influence on the space environment, surprisingly little is understood about the origin and behavior of δ-spots. In this paper, we perform a systematic study of the behavior of emerging flux ropes to test a theoretical model for the formation of δ-spots: the kink instability of emerging flux ropes. We simulated the emergence of highly twisted, kink-unstable flux ropes from the convection zone into the corona, and compared their photospheric properties to those of emerged weakly twisted, kink-stable flux ropes. We show that the photospheric manifestations of the emergence of highly twisted flux ropes closely match the observed properties of δ-spots, and we discuss the resulting implications for observations. Our results strongly support and extend previous theoretical work that suggested that the kink instability of emerging flux ropes is a promising candidate to explain δ-spot formation, as it reproduces their key characteristics very well.

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Section: Photospheric Evolutionmentioning

confidence: 94%

The Role of Twist in Kinked Flux Rope Emergence and Delta-spot Formation

Knizhnik

Linton

DeVore

2018

ApJ

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“…We use the same temporal and morphological criteria to select ARs as described in Poisson et al (2015a). The sample consists of ARs with a low background flux, whose emergence phase is observed during their transit across the solar disc.…”

Section: Data Usedmentioning

confidence: 99%

“…In Poisson et al (2015a) we presented a systematic method to quantify the influence of magnetic tongues using the evolution of the photospheric inversion line (PIL) during the emergence of bipolar ARs. We measure the acute angle between the estimated PIL and the line orthogonal to the AR bipole axis.…”

Section: Introductionmentioning

confidence: 99%

Correcting the effect of magnetic tongues on the tilt angle of bipolar active regions

Poisson

Fuentes

Mandrini

et al. 2020

A&A

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Context. The magnetic polarities of bipolar active regions (ARs) exhibit elongations in line-of-sight magnetograms during their emergence. These elongations are referred to as magnetic tongues and attributed to the presence of twist in the emerging magnetic flux-ropes (FRs) that form ARs. Aims. The presence of magnetic tongues affects the measurement of any AR characteristic that depends on its magnetic flux distribution. The AR tilt-angle is one of them. We aim to develop a method to isolate and remove the flux associated with the tongues to determine the AR tilt-angle with as much precision as possible. Methods. As a first approach, we used a simple emergence model of a FR. This allowed us to develop and test our aim based on a method to remove the effects of magnetic tongues. Then, using the experience gained from the analysis of the model, we applied our method to photospheric observations of bipolar ARs that show clear magnetic tongues. Results. Using the developed procedure on the FR model, we can reduce the deviation in the tilt estimation by more than 60%. Next we illustrate the performance of the method with four examples of bipolar ARs selected for their large magnetic tongues. The new method efficiently removes the spurious rotation of the bipole. This correction is mostly independent of the method input parameters and significant since it is larger than all the estimated tilt errors. Conclusions. We have developed a method to isolate the magnetic flux associated with the FR core during the emergence of bipolar ARs. This allows us to compute the AR tilt-angle and its evolution as precisely as possible. We suggest that the high dispersion observed in the determination of AR tilt-angles in studies that massively compute them from line-of sight magnetograms can be partly due to the existence of magnetic tongues whose presence is not sufficiently acknowledged.

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“…and electric currents associated to such a nonpotential field, e.g. Rust and Kumar (1996); McKenzie and Canfield (2008); Koleva et al (2012); Jiang et al (2014); Poisson et al (2015b). Abrupt magnetic reconfigurations, associated to the reconnection of field lines, transform large amounts of the free magnetic energy stored in the coronal field into kinetic and thermal energy, powering eruptive events such as CMEs and flares, e.g.…”

Section: Introductionmentioning

confidence: 99%

Analysis of a long-duration AR throughout five solar rotations: Magnetic properties and ejective events

Iglesias

Cremades

Merenda

et al. 2020

Advances in Space Research

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Coronal mass ejections (CMEs), which are among the most magnificent solar eruptions, are a major driver of space weather and can thus affect diverse human technologies. Different processes have been proposed to explain the initiation and release of CMEs from solar active regions (ARs), without reaching consensus on which is the predominant scenario, and thus rendering impossible to accurately predict when a CME is going to erupt from a given AR. To investigate AR magnetic properties that favor CMEs production, we employ multi-spacecraft data to analyze a long duration AR (NOAA 11089, 11100, 11106, 11112 and 11121) throughout its complete lifetime, spanning five Carrington rotations from July to November 2010. We use data from the Solar Dynamics Observatory to study the evolution of the AR magnetic properties during the five near-side passages, and a proxy to follow the magnetic flux changes when no magnetograms are available, i.e. during farside transits. The ejectivity is studied by characterizing the angular widths, speeds and masses of 108 CMEs that we associated to the AR, when examining a 124-day period. Such an ejectivity tracking was possible thanks to the mulit-viewpoint images provided by the Solar-Terrestrial Relations Observatory and Solar and Heliospheric Observatory in a quasi-quadrature configuration. We also inspected the X-ray flares registered by the GOES satellite and found 162 to be associated to the AR under study. Given the substantial number of ejections studied, we use a statistical approach instead of a single-event analysis. We found three well defined periods of very high CMEs activity and two periods with no mass ejections that are preceded or accompanied by characteristic changes in the AR magnetic flux, free magnetic energy and/or presence of electric currents. Our large sample of CMEs and long term study of a single AR, provide further evidence relating AR magnetic activity to CME and Flare production.

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Active-Region Twist Derived from Magnetic Tongues and Linear Force-Free Extrapolations

Cited by 13 publications

References 35 publications

The Role of Twist in Kinked Flux Rope Emergence and Delta-spot Formation

The Role of Twist in Kinked Flux Rope Emergence and Delta-spot Formation

Correcting the effect of magnetic tongues on the tilt angle of bipolar active regions

Analysis of a long-duration AR throughout five solar rotations: Magnetic properties and ejective events

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