Segmentation of Coronal Holes Using Active Contours Without Edges

Boucheron, Laura E.; Valluri, M.; McAteer, R. T. James

doi:10.1007/s11207-016-0985-z

Cited by 23 publications

(9 citation statements)

References 30 publications

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“…Because of their high contrast between coronal holes and quiet Sun regions, these filtergrams are often used to identify coronal holes in EUV images by various segmentation techniques (e.g. Krista & Gallagher 2009;Rotter et al 2012;Verbeeck et al 2014;Lowder et al 2014;Caplan et al 2016;Boucheron et al 2016). The AIA 193 Å filtergrams observe emission from Fe XII ions in the coronal plasma at a temperature of about 1.6 MK (peak response).…”

Section: Datasets and Data Reduc-tionmentioning

confidence: 99%

Characteristics of Low-latitude Coronal Holes near the Maximum of Solar Cycle 24

Hofmeister

Veronig

Reiss

et al. 2017

ApJ

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We investigate the statistics of 288 low-latitude coronal holes extracted from SDO/AIA-193 filtergrams over the time range of2011 January 01-2013 December 31. We analyze the distribution of characteristic coronal hole properties, such as the areas, mean AIA-193 intensities, and mean magnetic field densities, the local distribution of the SDO/AIA-193 intensity and the magnetic field within the coronal holes, and the distribution of magnetic flux tubes in coronal holes. We find that the mean magnetic field density of all coronal holes under study is 3.0±1.6 G, and the percentaged unbalanced magnetic flux is 49±16%. The mean magnetic field density, the mean unsigned magnetic field density, and the percentaged unbalanced magnetic flux of coronal holes depend strongly pairwise on each other, with correlation coefficients cc>0.92. Furthermore, we find that the unbalanced magnetic flux of the coronal holes is predominantly concentrated in magnetic flux tubes: 38% (81%) of the unbalanced magnetic flux of coronal holes arises from only 1% (10%) of the coronal hole area, clustered in magnetic flux tubes with field strengths >50 G (10 G). The average magnetic field density and the unbalanced magnetic flux derived from the magnetic flux tubes correlate with the mean magnetic field density and the unbalanced magnetic flux of the overall coronal hole (cc>0.93). These findings give evidence that the overall magnetic characteristics of coronal holes are governed by the characteristics of the magnetic flux tubes.

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Section: Datasets and Data Reduc-tionmentioning

confidence: 99%

Characteristics of Low-latitude Coronal Holes near the Maximum of Solar Cycle 24

Hofmeister

Veronig

Reiss

et al. 2017

ApJ

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“…The identification of CH regions is traditionally performed by visual inspection of image data (Harvey & Recely 2002). In recent years, several automatic or semi-automatic routines have been developed for more objective results (Henney & Harvey 2005;Scholl & Habbal 2008;Krista & Gallagher 2009;Rotter et al 2012;Lowder et al 2014;Verbeeck et al 2014;Boucheron et al 2016;Caplan et al 2016;Garton et al 2018;Heinemann et al 2019). In combination with photospheric magnetic field data, the extracted CH area can be used to derive the open magnetic flux from that region.…”

Section: Introductionmentioning

confidence: 99%

Coronal Hole Detection and Open Magnetic Flux

Linker

Heinemann

Temmer

et al. 2021

ApJ

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Many scientists use coronal hole (CH) detections to infer open magnetic flux. Detection techniques differ in the areas that they assign as open, and may obtain different values for the open magnetic flux. We characterize the uncertainties of these methods, by applying six different detection methods to deduce the area and open flux of a near-disk center CH observed on 2010 September 19, and applying a single method to five different EUV filtergrams for this CH. Open flux was calculated using five different magnetic maps. The standard deviation (interpreted as the uncertainty) in the open flux estimate for this CH ≈ 26%. However, including the variability of different magnetic data sources, this uncertainty almost doubles to 45%. We use two of the methods to characterize the area and open flux for all CHs in this time period. We find that the open flux is greatly underestimated compared to values inferred from in situ measurements (by 2.2-4 times). We also test our detection techniques on simulated emission images from a thermodynamic MHD model of the solar corona. We find that the methods overestimate the area and open flux in the simulated CH, but the average error in the flux is only about 7%. The full-Sun detections on the simulated corona underestimate the model open flux, but by factors well below what is needed to account for the missing flux in the observations. Under-detection of open flux in coronal holes likely contributes to the recognized deficit in solar open flux, but is unlikely to resolve it.

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“…However, there is another observational constraint on the modelsthe predicted open field regions should match CHs observed in emission. While such comparisons have generally been qualitative, the advent of automated CH detection algorithms (Henney & Harvey 2005;Scholl & Habbal 2008;Krista & Gallagher 2009;Lowder et al 2014;Verbeeck et al 2014;Boucheron et al 2016;Caplan et al 2016) opens the door for more objective comparisons. Lowder et al (2014) performed a comprehensive study of open flux from automatically detected CHs for the 1996-2013 time period, using data from the Solar and Heliospheric Observatory (SOHO) Extreme Ultraviolet Imaging Telescope (EIT), the Solar Terrestrial Relations Observatory (STEREO) Extreme Ultraviolet Imager (EUVI), and the Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) to detect CHs.…”

Section: Introductionmentioning

confidence: 99%

The Open Flux Problem

Linker

Caplan

Downs

et al. 2017

ApJ

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189

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractThe heliospheric magnetic field is of pivotal importance in solar and space physics. The field is rooted in the Sun's photosphere, where it has been observed for many years. Global maps of the solar magnetic field based on full-disk magnetograms are commonly used as boundary conditions for coronal and solar wind models. Two primary observational constraints on the models are (1) the open field regions in the model should approximately correspond to coronal holes (CHs) observed in emission and (2) the magnitude of the open magnetic flux in the model should match that inferred from in situ spacecraft measurements. In this study, we calculate both magnetohydrodynamic and potential field source surface solutions using 14 different magnetic maps produced from five different types of observatory magnetograms, for the time period surrounding 2010 July. We have found that for all of the model/map combinations, models that have CH areas close to observations underestimate the interplanetary magnetic flux, or, conversely, for models to match the interplanetary flux, the modeled open field regions are larger than CHs observed in EUV emission. In an alternative approach, we estimate the open magnetic flux entirely from solar observations by combining automatically detected CHs for Carrington rotation 2098 with observatory synoptic magnetic maps. This approach also underestimates the interplanetary magnetic flux. Our results imply that either typical observatory maps underestimate the Sun's magnetic flux, or a significant portion of the open magnetic flux is not rooted in regions that are obviously dark in EUV and X-ray emission.

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Segmentation of Coronal Holes Using Active Contours Without Edges

Cited by 23 publications

References 30 publications

Characteristics of Low-latitude Coronal Holes near the Maximum of Solar Cycle 24

Characteristics of Low-latitude Coronal Holes near the Maximum of Solar Cycle 24

Coronal Hole Detection and Open Magnetic Flux

The Open Flux Problem

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