Energetics of Solar Coronal Bright Points

Rad, Somaye Hosseini; Alipour, Nasibe; Safari, Hossein

doi:10.3847/1538-4357/abc8e8

Cited by 13 publications

(11 citation statements)

References 93 publications

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“…The power law index (for peak intensity and total intensity of campfires as a class of small-scale events) greater than 2 is in agreement with the previous findings for energetic events (e.g., Krucker & Benz 1998;Pauluhn & Solanki 2007b;Bazarghan et al 2008;Tajfirouze & Safari 2012;Reale 2014). Furthermore, the power law index of about 2.7 for the peak intensity distribution of campfires is in the range of indices obtained for the distribution of energy-loss flux of CBPs (Hosseini Rad et al 2021). Generally, however, when deriving a power law index, there are error sources such as the instrument sensitivity, performance of a feature detection method (identification and tracking), estimation of modeling parameters, and the specific time of observations at a solar cycle (e.g., Parnell & Jupp 2000;Parnell 2002;Hosseini Rad et al 2021).…”

Section: Hri Euv Brighteningssupporting

confidence: 51%

“…Furthermore, the power law index of about 2.7 for the peak intensity distribution of campfires is in the range of indices obtained for the distribution of energy-loss flux of CBPs (Hosseini Rad et al 2021). Generally, however, when deriving a power law index, there are error sources such as the instrument sensitivity, performance of a feature detection method (identification and tracking), estimation of modeling parameters, and the specific time of observations at a solar cycle (e.g., Parnell & Jupp 2000;Parnell 2002;Hosseini Rad et al 2021). An accurate determination of the power law index for the energy distribution of flaring-like instabilities (from picoflares to large X-class flares) and their generating mechanisms is still an open problem (Verbeeck et al 2019).…”

Section: Hri Euv Brighteningssupporting

confidence: 51%

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Automatic detection of small-scale EUV brightenings observed by the Solar Orbiter/EUI

Alipour,

Safari,

Verbeeck

et al. 2022

Preprint

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Context. Accurate detections of frequent small-scale extreme ultraviolet (EUV) brightenings are essential to the investigation of the physical processes heating the corona. Aims. We detected small-scale brightenings, termed campfires, using their morphological and intensity structures as observed in coronal EUV imaging observations for statistical analysis. Methods. We applied a method based on Zernike moments and a support vector machine (SVM) classifier to automatically identify and track campfires observed by Solar Orbiter/Extreme Ultraviolet Imager (EUI) and Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA). Results. This method detected 8678 campfires (with length scales between 400 km and 4000 km) from a sequence of 50 High Resolution EUV telescope (HRI EUV ) 174 Å images. From 21 near co-temporal AIA images covering the same field of view as EUI, we found 1131 campfires, 58% of which were also detected in HRI EUV images. In contrast, about 16% of campfires recognized in HRI EUV were detected by AIA. We obtain a campfire birthrate of 2 × 10 −16 m −2 s −1 . About 40% of campfires show a duration longer than 5 s, having been observed in at least two HRI EUV images. We find that 27% of campfires were found in coronal bright points and the remaining 73% have occurred out of coronal bright points. We detected 23 EUI campfires with a duration greater than 245 s. We found that about 80% of campfires are formed at supergranular boundaries, and the features with the highest total intensities are generated at network junctions and intense H I Lyman-α emission regions observed by EUI/HRI Lya . The probability distribution functions for the total intensity, peak intensity, and projected area of campfires follow a power law behavior with absolute indices between 2 and 3. This self-similar behavior is a possible signature of self-organization, or even self-organized criticality, in the campfire formation process.

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Section: Hri Euv Brighteningssupporting

confidence: 51%

Section: Hri Euv Brighteningssupporting

confidence: 51%

Automatic detection of small-scale EUV brightenings observed by the Solar Orbiter/EUI

Alipour,

Safari,

Verbeeck

et al. 2022

Preprint

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“…We note that the field strength is the average along the loop, without considering the change of density with height. For most oscillation events, the estimated magnetic fields are rather small, just around 1-3 G. However, previous measurements of the CBP electron densities show a range of 10 15 -10 16 m −3 (Madjarska 2019;Hosseini Rad et al 2021). Meanwhile, as mentioned in Section 4.1, we are likely to underestimate the loop length, which will lead to an underestimation of the kink speed, the Alfvén speed, and consequently the magnetic field strength.…”

Section: 6 I I W Rnmentioning

confidence: 81%

Decayless Oscillations in Solar Coronal Bright Points

Gao

Doorsselaere

Chen

2022

ApJ

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Decayless kink oscillations of solar coronal loops (or decayless oscillations for short) have attracted great attention since their discovery. Coronal bright points (CBPs) are mini-active regions and consist of loops with a small size. However, decayless oscillations in CBPs have not been widely reported. In this study, we identified this kind of oscillations in some CBPs using 171 Å images taken by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory. After using the motion magnification algorithm to increase oscillation amplitudes, we made time–distance maps to identify the oscillatory signals. We also estimated the loop lengths and velocity amplitudes. We analyzed 23 CBPs and found 31 oscillation events in 16 of them. The oscillation periods range from 1 to 8 minutes (on average about 5 minutes), and the displacement amplitudes have an average value of 0.07 Mm. The average loop length and velocity amplitude are 23 Mm and 1.57 km s−1, respectively. Relationships between different oscillation parameters are also examined. Additionally, we performed a simple model to illustrate how these subpixel oscillation amplitudes (less than 0.4 Mm) could be detected. Results of the model confirm the reliability of our data processing methods. Our study shows for the first time that decayless oscillations are common in small-scale loops of CBPs. These oscillations allow for seismological diagnostics of the Alfvén speed and magnetic field strength in the corona.

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“…Quasiperiodic oscillations with periods from minutes to hours are also reported in CBPs (Tian et al 2008;Samanta et al 2015). CBPs can be found everywhere at the solar atmosphere and appear significantly to coincide with magnetic neutral lines, which should play an important role for understanding the coronal heating (Priest et al 1994;Shibata et al 2007;Tian et al 2007;Hosseini Rad et al 2021).…”

Section: Introductionmentioning

confidence: 80%

Moving structures in ultraviolet bright points: observations from Solar Orbiter/EUI

2022

Preprint

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Context. Moving structures have been detected in coronal bright points and in a solar flare in active regions, which were bi-directional, symmetrical, simultaneous, and quasi-periodic (Ning & Guo 2014;Ning 2016;Li et al. 2016a). They could be regarded as observational evidence of plasma outflows via magnetic reconnection. Aims. We explored pairs of moving structures in fifteen ultraviolet bright points (UBPs), which were observed in the quiet Sun or inside a small active region on 19 November 2020. Methods. The UBPs were measured by the High Resolution (HRI) Telescopes of the Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter (SolO) in two passbands, HRI EUV 174 Å and HRI Lyα 1216 Å. The pairs of moving structures are identified in timedistance slices along curved slits of UBPs, and their quasi-periods are determined from the fast Fourier transform and wavelet analysis method.Results. Moving structures observed in ten UBPs as starting from their bright cores and propagating toward two ends, are interpreted as diverging motions of bi-directional moving structures. These moving structures are also characterized by simultaneity and symmetry and in the case of seven UBPs they exhibit quasi-periodicity. Moving structures seen in another five UBPs as originating from double ends and moving closer, and merging together, are manifested as converging motions. A sympathetic UBP induced by the primary UBP is observed at the edge of a small active region, and their moving structures also show the converging motion. Conclusions. The diverging motions of bi-directional moving structures could be generated by outflows after magnetic reconnections. The converging motions of two moving structures might be caused by inflows through the magnetic reconnection, or might be interpreted as upflows driven by the chromospheric evaporation.

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Energetics of Solar Coronal Bright Points

Cited by 13 publications

References 93 publications

Automatic detection of small-scale EUV brightenings observed by the Solar Orbiter/EUI

Automatic detection of small-scale EUV brightenings observed by the Solar Orbiter/EUI

Decayless Oscillations in Solar Coronal Bright Points

Moving structures in ultraviolet bright points: observations from Solar Orbiter/EUI

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