The chromospheric component of coronal bright points

Madjarska, M. S.; Chae, Jongchul; Moreno‐Insertis, F.; Hou, Zhenyong; Nóbrega-Siverio, Daniel; Kwak, Hannah; Galsgaard, K.; Cho, Kyuhyoun

doi:10.1051/0004-6361/202039329

Cited by 15 publications

(26 citation statements)

References 51 publications

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“…The correlation between small-scale ALMA bright features and the Hα wing sum dark features is good (all cases except ID = 6, where the feature appears bright), although the shape is not completely preserved, which could be a consequence of lower resolution. Dark fibrils in the Hα wing might mark horizontal field lines connecting opposite magnetic polarities (Zirin 1988;Madjarska et al 2021). This is in agreement with a high correlation of ALMA bright points and magnetic structures, although in some cases only one polarity could be related to the mm and Hα structure.…”

Section: A Comparison Of Small-scale Alma Bright Features With Struct...supporting

confidence: 53%

ALMA small-scale features in the quiet Sun and active regions

Brajša

Skokić

Sudar

et al. 2021

A&A

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Aims. The main aim of the present analysis is to decipher (i) the small-scale bright features in solar images of the quiet Sun and active regions obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) and (ii) the ALMA correspondence of various known chromospheric structures visible in the Hα images of the Sun. Methods. Small-scale ALMA bright features in the quiet Sun region were analyzed using single-dish ALMA observations (1.21 mm, 248 GHz) and in an active region using interferometric ALMA measurements (3 mm, 100 GHz). With the single-dish observations, a full-disk solar image is produced, while interferometric measurements enable the high-resolution reconstruction of part of the solar disk, including the active region. The selected quiet Sun and active regions are compared with the Hα (core and wing sum), EUV, and soft X-ray images and with the magnetograms. Results. In the quiet Sun region, enhanced emission seen in the ALMA is almost always associated with a strong line-of-sight magnetic field. Four coronal bright points were identified, while other small-scale ALMA bright features are most likely associated with magnetic network elements and plages. In the active region, in 14 small-scale ALMA bright features randomly selected and compared with other images, we found five good candidates for coronal bright points, two for plages, and five for fibrils. Two unclear cases remain: a fibril or a jet, and a coronal bright point or a plage. A comparison of the Hα core image and the 3 mm ALMA image of the analyzed active region showed that the sunspot appears dark in both images (with a local ALMA radiation enhancement in sunspot umbra), the four plage areas are bright in both images and dark small Hα filaments are clearly recognized as dark structures of the same shape also in ALMA.

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Section: A Comparison Of Small-scale Alma Bright Features With Struct...supporting

confidence: 53%

ALMA small-scale features in the quiet Sun and active regions

Brajša

Skokić

Sudar

et al. 2021

A&A

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“…In addition, magnetic flux cancellation and emergence events were almost always taking place in connection with CBPs (e.g. Harvey et al 1999;Madjarska et al 2003;Zhang et al 2012;Huang et al 2012;Zhang et al 2014;Mou et al 2016;Madjarska et al 2021). Cancellation and the associated magnetic reconnection in the lower atmosphere were observed at the footpoints of hotter coronal loops in active regions as well (e.g.…”

Section: Discussionmentioning

confidence: 98%

The magnetic drivers of campfires seen by the Polarimetric and Helioseismic Imager (PHI) on Solar Orbiter

Kahil

Hirzberger

Solanki

et al. 2022

A&A

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Context. The Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter (SO) spacecraft observed small extreme ultraviolet (EUV) bursts, termed campfires, that have been proposed to be brightenings near the apexes of low-lying loops in the quiet-Sun atmosphere. The underlying magnetic processes driving these campfires are not understood. Aims. During the cruise phase of SO and at a distance of 0.523 AU from the Sun, the Polarimetric and Helioseismic Imager on Solar Orbiter (SO/PHI) observed a quiet-Sun region jointly with SO/EUI, offering the possibility to investigate the surface magnetic field dynamics underlying campfires at a spatial resolution of about 380 km. Methods. We used co-spatial and co-temporal data of the quiet-Sun network at disc centre acquired with the High Resolution Imager of SO/EUI at 17.4 nm (HRI EUV , cadence 2 s) and the High Resolution Telescope of SO/PHI at 617.3 nm (HRT, cadence 2.5 min). Campfires that are within the SO/PHI−SO/EUI common field of view were isolated and categorised according to the underlying magnetic activity. Results. In 71% of the 38 isolated events, campfires are confined between bipolar magnetic features, which seem to exhibit signatures of magnetic flux cancellation. The flux cancellation occurs either between the two main footpoints, or between one of the footpoints of the loop housing the campfire and a nearby opposite polarity patch. In one particularly clear-cut case, we detected the emergence of a small-scale magnetic loop in the internetwork followed soon afterwards by a campfire brightening adjacent to the location of the linear polarisation signal in the photosphere, that is to say near where the apex of the emerging loop lays. The rest of the events were observed over small scattered magnetic features, which could not be identified as magnetic footpoints of the campfire hosting loops. Conclusions. The majority of campfires could be driven by magnetic reconnection triggered at the footpoints, similar to the physical processes occurring in the burst-like EUV events discussed in the literature. About a quarter of all analysed campfires, however, are not associated to such magnetic activity in the photosphere, which implies that other heating mechanisms are energising these small-scale EUV brightenings.

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“…The correlation between small-scale ALMA bright features and Hα wing sum dark features is very high, as it was confirmed in all but one case. Dark fibrils in the Hα wing might mark horizontal field lines connecting opposite magnetic polarities (Zirin 1988;Madjarska et al 2021), but the fibrils might also show significant dynamics and magnetic evolution, as pointed out by Tandberg-Hanssen (1995).…”

Section: Discussionmentioning

confidence: 99%

ALMA small-scale features in the quiet Sun and active regions

Brajsa,

Skokic,

Sudar

et al. 2021

Preprint

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Aims. The main aim of the present analysis is to decipher (i) the small-scale bright features in solar images of the quiet Sun and active regions obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) and (ii) the ALMA correspondence of various known chromospheric structures visible in the Hα images of the Sun. Methods. Small-scale ALMA bright features in the quiet Sun region were analyzed using single-dish ALMA observations (1.21 mm, 248 GHz) and in an active region using interferometric ALMA measurements (3 mm, 100 GHz). With the single-dish observations, a full-disk solar image is produced, while interferometric measurements enable the high-resolution reconstruction of part of the solar disk, including the active region. The selected quiet Sun and active regions are compared with the Hα (core and wing sum), EUV, and soft X-ray images and with the magnetograms. Results. In the quiet Sun region, enhanced emission seen in the ALMA is almost always associated with a strong line-of-sight (LOS) magnetic field. Four coronal bright points were identified, while other small-scale ALMA bright features are most likely associated with magnetic network elements and plages. In the active region, in 14 small-scale ALMA bright features randomly selected and compared with other images, we found five good candidates for coronal bright points, two for plages, and five for fibrils. Two unclear cases remain: a fibril or a jet, and a coronal bright point or a plage. A comparison of the Hα core image and the 3 mm ALMA image of the analyzed active region showed that the sunspot appears dark in both images (with a local ALMA radiation enhancement in sunspot umbra), the four plage areas are bright in both images and dark small Hα filaments are clearly recognized as dark structures of the same shape also in ALMA.

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The chromospheric component of coronal bright points

Cited by 15 publications

References 51 publications

ALMA small-scale features in the quiet Sun and active regions

ALMA small-scale features in the quiet Sun and active regions

The magnetic drivers of campfires seen by the Polarimetric and Helioseismic Imager (PHI) on Solar Orbiter

ALMA small-scale features in the quiet Sun and active regions

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