Objective magnetic vortex detection

Rempel, Erico L.; Gomes, Tiago F P; Silva, Suzana S. A.; Chian, Abraham C.‐L.

doi:10.1103/physreve.99.043206

Cited by 11 publications

(9 citation statements)

References 43 publications

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“…In turn, the magnetic field is also impacted by the vortices' dynamics, leading to torsion and bending of the magnetic field. For the 17 analyzed solar vortices, only #12 had a magnetic vortex as defined by Rempel et al (2019) and which is cospatially existing with the kinematic solar vortex tube. Those results are in accordance with the findings of Moll et al (2012), who show that the magnetic field lines tend to expand with height and do not present significant twisting.…”

Section: Discussionmentioning

confidence: 99%

Solar Vortex Tubes: Vortex Dynamics in the Solar Atmosphere

Silva

Fedun

Verth

et al. 2020

ApJ

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In this work, a state-of-the-art vortex detection method, Instantaneous Vorticity Deviation, is applied to locate three-dimensional vortex tube boundaries in numerical simulations of solar photospheric magnetoconvection performed by the MURaM code. We detected three-dimensional vortices distributed along intergranular regions and displaying coned shapes that extend from the photosphere to the low chromosphere. Based on a well-defined vortex center and boundary, we were able to determine averaged radial profiles and thereby investigate the dynamics across the vortical flows at different height levels. The solar vortex tubes present nonuniform angular rotational velocity, and, at all height levels, there are eddy viscosity effects within the vortices, which slow down the plasma as it moves toward the center. The vortices impact the magnetic field as they help to intensify the magnetic field at the sinking points, and in turn, the magnetic field ends up playing an essential role in the vortex dynamics. The magnetic field was found to be especially important to the vorticity evolution. On the other hand, it is shown that, in general, kinematic vortices do not give rise to magnetic vortices unless their tangential velocities at different height levels are high enough to overcome the magnetic tension.

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Section: Discussionmentioning

confidence: 99%

Solar Vortex Tubes: Vortex Dynamics in the Solar Atmosphere

Silva

Fedun

Verth

et al. 2020

ApJ

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“…Next, we define the M -vortex boundary by identifying the region where the topology of magnetic field lines defines a coherent twisted magnetic flux tube. Defining of M -vortex as a coherent structure of the magnetic field can be done using the Instantaneous Averaged Current Deviation (IACD) method (Rempel et al 2019). The IACD field is defined as…”

Section: Methodsmentioning

confidence: 99%

“…Thereby, we name such structures magnetic vortices, and we introduce a formal definition that enables a proper three-dimensional vortex identification. Both the vortex definition and detection are based on a recently developed method to detect magnetic vortex boundaries which precisely defines the region where the magnetic field lines have the topology of a magnetic flux tube (Rempel et al 2017(Rempel et al , 2019. We apply kinetic and magnetic vortex detection methods to realistic radiative magneto-convection simulations and analyze the plasma within magnetic vortices and those structures' lifetime.…”

Section: Introductionmentioning

confidence: 99%

Solar Vortex Tubes. II. On the Origin of Magnetic Vortices

Silva

Verth

Rempel

et al. 2021

ApJ

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The solar atmosphere presents a wealth of dynamics due to a constant interplay between the plasma flows and magnetic fields. Twisted flux tubes are an essential magnetic structure, believed to be driven by rotational surface's motions and linked to plasma heating, jets and eruptive phenomena. Despite extensive investigations, twisted magnetic flux tubes lack a proper mathematical definition, precluding their automatic detection. This work addresses this issue by defining them as magnetic vortices and introduces a formal definition which is based on a recently developed magnetic vortices detection technique, the Integrated Averaged Current Deviation method. We applied this method and kinetic vortices identification technique to realistic magneto-convection simulations obtained from the MURaM code. The preferential site for these two types of vortices is the intergranular downflow, but while the magnetic vortices are found mostly in the small areas where plasma-β > 1, the rotational flow structures, the kinetic vortices, were detected in locations where plasma-β < 1. The magnetic vortices locally concentrate the magnetic field's vertical components and current, lasting on average around a minute. Two types of magnetic vortices are introduced based on their magnetic to kinetic energy ratio. For the first type, the magnetic energy prevails, and the magnetic vortices are mostly vertical. The second type of magnetic vortices presents distinct shapes and a lower magnetic to kinetic energy ratio. We have found that magnetic vortices may appear if two conditions are simultaneously present: (i) shear flow, (ii) plasma-β > 1. The presence of rotational motion is not necessary.

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“…An LAVD-based approach was also used to detect kinematic vortices in a 3D magnetohydrodynamic (MHD) dynamo simulation by Rempel et al (2017) who proposed a new method for the detection of magnetic vortices and the determination of their boundaries based on the integrated averaged current deviation (IACD) integral. This method was later applied by Rempel et al (2019) on a series of 2D and 3D simulations.…”

Section: Introductionmentioning

confidence: 99%

Chromospheric swirls

Dakanalis

Tsiropoula

Tziotziou

et al. 2022

A&A

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Context. Chromospheric swirls are related to convectively driven vortex flows and considered to play a significant role in the dynamics and heating of the upper solar atmosphere. It is important to automatically detect and track them in chromospheric observations and determine their properties. Aims. We aim to detect and track chromospheric swirls both in space and time by applying a newly developed novel automated method on high quality time series of Hα observations and to conduct a statistical analysis to determine their properties. Methods. We applied a recently developed automated chromospheric swirl detection method to time-series observations of a quiet region of the solar chromosphere obtained in the Hα-0.2 Å wavelength of the Hα spectral line by the CRISP instrument at the Swedish 1-m Solar Telescope. The algorithm exploits the morphological characteristics of swirling events in high contrast chromospheric observations and results in the detection of these structures in each frame of the time series and their tracking over time. We conducted a statistical analysis to determine their various properties, including a survival analysis for deriving the mean lifetime. Results. A mean number of 146 ± 9 swirls was detected within the Hα-0.2 Å field of view at any given time. The mean surface density is found equal to ∼0.08 swirls Mm −2 and the occurrence rate is ∼10 −2 swirls Mm −2 min −1 . These values are much higher than those previously reported from chromospheric observations. The radii of the detected swirls range between 0.5 and 2.5 Mm, with a mean value equal to 1.3 ± 0.3 Mm, which is slightly higher than previous reports. The lifetimes range between 1.5 min and 33.7 min (equal to the duration of the observations) with an arithmetic mean value of ∼8.5 min. A survival analysis of the lifetimes, however, using the Kaplan-Meier estimator in combination with a parametric model results in a mean lifetime of 10.3 ± 0.6 min. Conclusions. Swirls are ubiquitous in the solar chromosphere. An automated method sheds more light on their abundance than visual inspection, while higher cadence, higher resolution observations will most probably result in the detection of a higher number of such features on smaller scales and with shorter lifetimes.

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Objective magnetic vortex detection

Cited by 11 publications

References 43 publications

Solar Vortex Tubes: Vortex Dynamics in the Solar Atmosphere

Solar Vortex Tubes: Vortex Dynamics in the Solar Atmosphere

Solar Vortex Tubes. II. On the Origin of Magnetic Vortices

Chromospheric swirls

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