Properties of Magnetic Tongues over a Solar Cycle

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

doi:10.1007/s11207-016-0926-x

Cited by 21 publications

(30 citation statements)

References 23 publications

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“…In Sect. 3, we tested CoFFE using an analytical model based on the kinematic rise of a half-torus FR (see Poisson et al 2016). Using this model we are able to study the evolution of the axial and the azimuthal fields separately and to compare them with the core and tongue locations provided by CoFFE.…”

Section: Discussionmentioning

confidence: 99%

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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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Section: Discussionmentioning

confidence: 99%

“…to minimise the contribution of the background magnetic flux (Poisson et al 2016). Movies for each AR were made to verify that the variable size box included all the magnetic flux of the AR at all times.…”

Section: Data Usedmentioning

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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“… 2011 ; Takizawa and Kitai 2015 ; Poisson et al. 2015 , 2016 ). Multiple observational studies showed that such yin-yang tongues are seen in flaring ARs, along with other observational characteristics including sigmoids, sheared coronal loops, and J-shaped flare ribbons (Li et al.…”

Section: Long-term and Large-scale Evolution: Observational Aspectsmentioning

confidence: 99%

Flare-productive active regions

Toriumi

Wang

2019

Living Rev Sol Phys

230

151

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Strong solar flares and coronal mass ejections, here defined not only as the bursts of electromagnetic radiation but as the entire process in which magnetic energy is released through magnetic reconnection and plasma instability, emanate from active regions (ARs) in which high magnetic non-potentiality resides in a wide variety of forms. This review focuses on the formation and evolution of flare-productive ARs from both observational and theoretical points of view. Starting from a general introduction of the genesis of ARs and solar flares, we give an overview of the key observational features during the long-term evolution in the pre-flare state, the rapid changes in the magnetic field associated with the flare occurrence, and the physical mechanisms behind these phenomena. Our picture of flare-productive ARs is summarized as follows: subject to the turbulent convection, the rising magnetic flux in the interior deforms into a complex structure and gains high non-potentiality; as the flux appears on the surface, an AR with large free magnetic energy and helicity is built, which is represented by -sunspots, sheared polarity inversion lines, magnetic flux ropes, etc; the flare occurs when sufficient magnetic energy has accumulated, and the drastic coronal evolution affects magnetic fields even in the photosphere. We show that the improvement of observational instruments and modeling capabilities has significantly advanced our understanding in the last decades. Finally, we discuss the outstanding issues and future perspective and further broaden our scope to the possible applications of our knowledge to space-weather forecasting, extreme events in history, and corresponding stellar activities. Electronic supplementary material The online version of this article (10.1007/s41116-019-0019-7) contains supplementary material, which is available to authorized users.

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“…The orientation of its magnetic fields is mostly West to East, although the presence of magnetic tongues leads to some deviation of the PIL orientation from that direction (Figure 1(c)). Following Poisson et al (2016), these tongues are interpreted as the contribution of the azimuthal field component of the emerging flux tube. They indicate a negative magnetic helicity, which is also suggested by the shear of the loops seen in the corona ( Figure 1(d)).…”

Section: Splitting Of the Eastern Filament Sectionmentioning

confidence: 99%

Sequential Eruptions Triggered by Flux Emergence: Observations and Modeling

Dacie

Török

Démoulin

et al. 2018

ApJ

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We describe and analyze observations by the Solar Dynamics Observatory of the emergence of a small, bipolar active region within an area of unipolar magnetic flux that was surrounded by a circular, quiescent filament. Within only eight hours of the start of the emergence, a partial splitting of the filament and two consecutive coronal mass ejections took place. We argue that all three dynamic events occurred as a result of particular magnetic-reconnection episodes between the emerging bipole and the pre-existing coronal magnetic field. In order to substantiate our interpretation, we consider three-dimensional magnetohydrodynamic simulations that model the emergence of magnetic flux in the vicinity of a large-scale coronal flux rope. The simulations qualitatively reproduce most of the reconnection episodes suggested by the observations; as well as the filament-splitting, the first eruption, and the formation of sheared/twisted fields that may have played a role in the second eruption. Our results suggest that the position of emerging flux with respect to the background magnetic configuration is a crucial factor for the resulting evolution, while previous results suggest that parameters such as the orientation or the amount of emerging flux are important as well. This poses a challenge for predicting the onset of eruptions that are triggered by flux emergence, and it calls for a detailed survey of the relevant parameter space by means of numerical simulations.

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Properties of Magnetic Tongues over a Solar Cycle

Cited by 21 publications

References 23 publications

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

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

Flare-productive active regions

Sequential Eruptions Triggered by Flux Emergence: Observations and Modeling

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