Evidence for two-loop interaction from IRIS and SDO observations of penumbral brightenings

Alissandrakis, C. E.; Koukras, Alexandros; Patsourakos, S.; Nindos, A.

doi:10.1051/0004-6361/201730643

Cited by 8 publications

(10 citation statements)

References 45 publications

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“…Here we focus on the observed morphology of the AIA 94 Å and 131 Å hot emission in each of these IRIS events, which suggests that the impulsive heating derives from large scale magnetic rearrangements/large angle reconnection. The interaction of small loops has been taken as explanation of a small flare observed with IRIS (Alissandrakis et al 2017), and our study provides direct evidence from the morphology observed in the hot AIA channels counterparts. Many recent papers have studied simultaneous observations from IRIS and SDO/AIA to investigate magnetic rearrangements causing localized brightenings in the transition region, and likely related with flux emergence (e.g., Jiang et al 2015;Toriumi et al 2017;Guglielmino et al 2018;Huang 2018;Tian et al 2018;Guglielmino et al 2019).…”

Section: Discussionsupporting

confidence: 65%

Impulsive Coronal Heating from Large-scale Magnetic Rearrangements: From IRIS to SDO/AIA

Reale

Testa

Petralia

et al. 2019

ApJ

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The Interface Region Imaging Spectrograph (IRIS) has observed bright spots at the transition region footpoints associated with heating in the overlying loops, as observed by coronal imagers. Some of these brightenings show significant blueshifts in the Si iv line at 1402.77Å (log T [K] ≈ 4.9). Such blueshifts cannot be reproduced by coronal loop models assuming heating by thermal conduction only, but are consistent with electron beam heating, highlighting for the first time the possible importance of non-thermal electrons in the heating of non-flaring active regions. Here we report on the coronal counterparts of these brightenings observed in the hot channels of the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. We show that the IRIS bright spots are the footpoints of very hot and transient coronal loops which clearly experience strong magnetic interactions and rearrangements, thus confirming the impulsive nature of the heating and providing important constraints for their physical interpretation.

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Section: Discussionsupporting

confidence: 65%

Impulsive Coronal Heating from Large-scale Magnetic Rearrangements: From IRIS to SDO/AIA

Reale

Testa

Petralia

et al. 2019

ApJ

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“…Direct evidence includes the detection of time variability of the intensity A&A 638, A62 (2020) (e.g., Berghmans et al 1998) or the emission measure (e.g., of clusters of pixels above some predefined threshold. In most studies, most of the detected events are spatially unresolved (e.g., Benz & Krucker 1999), but some events may exhibit a loop-like morphology (e.g., White et al 1995;Warren et al 2007), a jet-like morphology (e.g., Tian et al 2014;Alissandrakis et al 2015), show evidence of two-loop interactions (e.g., Shimizu et al 1994;Alissandrakis et al 2017a), or even resemble Ellerman bombs (e.g., Shetye et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Transient brightenings in the quiet Sun detected by ALMA at 3 mm

Nindos

Alissandrakis

Patsourakos

et al. 2020

A&A

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Aims. We investigate transient brightenings, that is, weak, small-scale episodes of energy release, in the quiet solar chromosphere; these episodes can provide insights into the heating mechanism of the outer layers of the solar atmosphere. Methods. Using Atacama Large Millimeter/submillimeter Array (ALMA) observations, we performed the first systematic survey for quiet Sun transient brightenings at 3 mm. Our dataset included images of six 87″ × 87″ fields of view of the quiet Sun obtained with angular resolution of a few arcsec at a cadence of 2 s. The transient brightenings were detected as weak enhancements above the average intensity after we removed the effect of the p-mode oscillations. A similar analysis, over the same fields of view, was performed for simultaneous 304 and 1600 Å data obtained with the Atmospheric Imaging Assembly. Results. We detected 184 3 mm transient brightening events with brightness temperatures from 70 K to more than 500 K above backgrounds of ∼7200 − 7450 K. All events showed light curves with a gradual rise and fall, strongly suggesting a thermal origin. Their mean duration and maximum area were 51.1 s and 12.3 Mm2, respectively, with a weak preference of appearing at network boundaries rather than in cell interiors. Both parameters exhibited power-law behavior with indices of 2.35 and 2.71, respectively. Only a small fraction of ALMA events had either 304 or 1600 Å counterparts but the properties of these events were not significantly different from those of the general population except that they lacked their low-end energy values. The total thermal energies of the ALMA transient brightenings were between 1.5 × 1024 and 9.9 × 1025 erg and their frequency distribution versus energy was a power law with an index of 1.67 ± 0.05. We found that the power per unit area provided by the ALMA events could account for only 1% of the chromospheric radiative losses (10% of the coronal ones). Conclusions. We were able to detect, for the first time, a significant number of weak 3 mm quiet Sun transient brightenings. However, their energy budget falls short of meeting the requirements for the heating of the upper layers of the solar atmosphere and this conclusion does not change even if we use the least restrictive criteria possible for the detection of transient brightenings.

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“…It has also observed that interaction between cool transition region loops could result in heating and then forming hotter coronal loops (e.g. Alissandrakis et al 2017;Yan et al 2018;Chitta et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Magnetic Loops above a Small Flux-emerging Region Observed by IRIS, Hinode, and SDO

Huang

2018

ApJ

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I report on observations of a set of magnetic loops above a region with late-phase flux emergence taken by IRIS, Hinode and SDO. The loop system consists of many transition region loop threads with size of 5-12 ′′ in length and ∼ 0.5 ′′ in width and coronal loops with similar length and ∼ 2 ′′ width. Although the loop system consists of threads with different temperatures, most individual loop thread have temperature in a narrow range. In the middle of the loop system, it shows clear systematic blue-shifts of about 10 km s −1 in the transition region that is consistent with a flux emerging picture, while red-shifts of about 10 km s −1 in the corona is observed. The nonthermal velocity of the loop system are smaller than the surrounding region in the transition region but are comparable in the corona. The electron densities of the coronal counterpart of the loop system range from 1 × 10 9 cm −3 to 4 × 10 9 cm −3 . Electron density of a transition region loop is also measured and found to be about 5 × 10 10 cm −3 , a magnitude larger than that in the coronal loops. In agreement with imaging data, the temperature profiles derived from the differential emission measurement technique confirms that some of the loops have been heated to corona. Our observations indicate that the flux emergence in its late phase is much different from that at the early stage. While the observed transition region is dominated by emerging flux, these emerging loops could be heated to corona and the heatings most likely take place only after they reaching the transition region or lower corona.

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Evidence for two-loop interaction from IRIS and SDO observations of penumbral brightenings

Cited by 8 publications

References 45 publications

Impulsive Coronal Heating from Large-scale Magnetic Rearrangements: From IRIS to SDO/AIA

Impulsive Coronal Heating from Large-scale Magnetic Rearrangements: From IRIS to SDO/AIA

Transient brightenings in the quiet Sun detected by ALMA at 3 mm

Magnetic Loops above a Small Flux-emerging Region Observed by IRIS, Hinode, and SDO

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