Emergence of small-scale magnetic flux in the quiet Sun

Kontogiannis, Ioannis; Tsiropoula, G.; Tziotziou, K.; Gontikakis, C.; Kuckein, C.; Verma, M.; Denker, C.

doi:10.1051/0004-6361/201936778

Cited by 12 publications

(6 citation statements)

References 84 publications

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“…Magnetic reconnection also may occur with U-loop emergences which cause brightenings in the local chromosphere (Gošić et al (2018), Kontogiannis et al (2020), and others). In order to investigate the effects of small-scale reconnection events on the higher layers of the atmosphere, we plan to combine observations in photospheric (as those employed in this study) and chromospheric lines.…”

Section: Discussionmentioning

confidence: 99%

Quantifying Properties of Photospheric Magnetic Cancellations in the Quiet Sun Internetwork

Ledvina¹,

Kazachenko²,

Criscuoli³

2022

ApJ

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We analyzed spectropolarimetric data from the Swedish 1 m Solar Telescope to investigate the physical properties of small-scale magnetic cancellations in the quiet Sun photosphere. Specifically, we looked at the full Stokes polarization profiles along the Fe i 557.6 nm and of the Fe i 630.1 nm lines measured by the CRisp Imaging SpectroPolarimeter to study the temporal evolution of the line-of-sight magnetic field during 42.5 minutes of quiet Sun evolution. From this magnetogram sequence, we visually identified 38 cancellation events. We then used the Yet Another Feature Tracking Algorithm to characterize the physical properties of these magnetic cancellations. We found on average 1.6 × 1016 Mx of magnetic flux canceled in each event with an average cancellation rate of 3.8 × 1014 Mx s−1. The derived canceled flux is associated with strong downflows, with an average speed of V LOS ≈ 1.1 km s−1. Our results show that the average lifetime of each event is 9.2 minutes with an average of 44.8% of initial magnetic flux being canceled. Our estimates of magnetic fluxes provide a lower limit since studied magnetic cancellation events have magnetic field values that are very close to the instrument noise level. We observed no horizontal magnetic fields at the cancellation sites and therefore cannot conclude whether the events are associated with structures that could cause magnetic reconnection.

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Section: Discussionmentioning

confidence: 99%

Quantifying Properties of Photospheric Magnetic Cancellations in the Quiet Sun Internetwork

Ledvina¹,

Kazachenko²,

Criscuoli³

2022

ApJ

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“…E.g., surges and EUV/X-ray jets with time delays of ∼ 5 − 10 min have been recorded (Schmieder et al 1994;Chae et al 1999;Alexander & Fletcher 1999;Jiang et al 2007). Also, hot and cool ejections can appear to be co-temporal and be either spatially offset or co-spatial (e.g., Mulay et al 2017;Kontogiannis et al 2020), or only cool ejections can form(e.g., surges, Ortiz et al 2020). We note further that similar energetic events at the feet of coronal loops could possibly create jet-like structures observed at these locations (Chitta et al 2017a,b).…”

Section: Discussionmentioning

confidence: 99%

A Cancellation Nanoflare Model for Solar Chromospheric and Coronal Heating. III. 3D Simulations and Atmospheric Response

Syntelis

Priest

2020

ApJ

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Inspired by recent observations suggesting that photospheric magnetic flux cancellation occurs much more frequently than previously thought, we analytically estimated the energy released from reconnection driven by photospheric flux cancellation, and proposed that it can act as a mechanism for chromospheric and coronal heating (Priest et al. 2018). Using two-dimensional simulations we validated the analytical estimates and studied the resulting atmospheric response (Syntelis et al. 2019). In the present work, we set up three-dimensional resistive MHD simulations of two cancelling polarities in a stratified atmosphere with a horizontal external field to further validate and improve upon the analytical estimates. The computational evaluation of the parameters associated with the energy release are in good qualitative agreement with the analytical estimates. The computational Poynting energy flux into the current sheet is in good qualitative agreement with the analytical estimates, after correcting the analytical expression to better account for the horizontal extent of the current sheet. The atmospheric response to the cancellation is the formation of hot ejections, cool ejections, or a combination of both hot and cool ejections, which can appear with a time difference and/or be spatially offset, depending on the properties of the cancelling region and the resulting height of the reconnection. Therefore, during the cancellation, a wide spectrum of ejections can be formed, which can account for the variety of multi-thermal ejections associated with Ellerman bombs, UV bursts and IRIS bombs, and also other ejections associated with small-scale cancelling regions and spicules.

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“…The emerging ephemeral regions appear in the solar corona as an X-ray bright point, also known as a coronal bright point (CBP; Vaiana et al 1973;Golub et al 1974Golub et al , 1977. These are small bipolar regions of ∼40″, live less than 24 hr, and at a given time have an absolute magnetic flux of 10 20 Mx or less (Harvey & Martin 1973;Hagenaar 2001;Kontogiannis et al 2020). Some CBPs might form by magnetic flux convergence and cancellation (Priest et al 1994;Longcope & Kankelborg 1999).…”

Section: Introductionmentioning

confidence: 99%

SolO/EUI Observations of Ubiquitous Fine-scale Bright Dots in an Emerging Flux Region: Comparison with a Bifrost MHD Simulation

Tiwari

Hansteen

Pontieu

et al. 2022

ApJ

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We report on the presence of numerous tiny bright dots in and around an emerging flux region (an X-ray/coronal bright point) observed with SolO’s EUI/HRIEUV in 174 Å. These dots are roundish and have a diameter of 675 ± 300 km, a lifetime of 50 ± 35 s, and an intensity enhancement of 30% ± 10% above their immediate surroundings. About half of the dots remain isolated during their evolution and move randomly and slowly (<10 km s−1). The other half show extensions, appearing as a small loop or surge/jet, with intensity propagations below 30 km s−1. Many of the bigger and brighter HRIEUV dots are discernible in the SDO/AIA 171 Å channel, have significant emissivity in the temperature range of 1–2 MK, and are often located at polarity inversion lines observed in SDO/HMI LOS magnetograms. Although not as pervasive as in observations, a Bifrost MHD simulation of an emerging flux region does show dots in synthetic Fe ix/x images. These dots in the simulation show distinct Doppler signatures—blueshifts and redshifts coexist, or a redshift of the order of 10 km s−1 is followed by a blueshift of similar or higher magnitude. The synthetic images of O v/vi and Si iv lines, which represent transition region radiation, also show the dots that are observed in Fe ix/x images, often expanded in size, or extended as a loop, and always with stronger Doppler velocities (up to 100 km s−1) than that in Fe ix/x lines. Our observation and simulation results, together with the field geometry of dots in the simulation, suggest that most dots in emerging flux regions form in the lower solar atmosphere (at ≈ 1 Mm) by magnetic reconnection between emerging and preexisting/emerged magnetic field. Some dots might be manifestations of magnetoacoustic shocks through the line formation region of Fe ix/x emission.

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Emergence of small-scale magnetic flux in the quiet Sun

Cited by 12 publications

References 84 publications

Quantifying Properties of Photospheric Magnetic Cancellations in the Quiet Sun Internetwork

Quantifying Properties of Photospheric Magnetic Cancellations in the Quiet Sun Internetwork

A Cancellation Nanoflare Model for Solar Chromospheric and Coronal Heating. III. 3D Simulations and Atmospheric Response

SolO/EUI Observations of Ubiquitous Fine-scale Bright Dots in an Emerging Flux Region: Comparison with a Bifrost MHD Simulation

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