Estimating Total Open Heliospheric Magnetic Flux

Wallace, Samantha; Arge, C. N.; Pattichis, Marios S.; Hock-Mysliwiec, Rachel; Henney, C. J.

doi:10.1007/s11207-019-1402-1

Cited by 61 publications

(92 citation statements)

References 58 publications

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“…The daily averaged results obtained with the GONG synoptic maps are smoothed over 27 days. As is known, there are disagreements between observed and modeled CHs and open magnetic flux (see, e.g., Linker et al, ; Lowder et al, , ; Wallace et al, ). This is a subject of ongoing research activities.…”

Section: Resultsmentioning

confidence: 99%

On Solutions of the PFSS Model With GONG Synoptic Maps for 2006–2018

Nikolić

2019

Space Weather

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The potential field source surface (PFSS) model is widely used to derive the magnetic field of the solar corona. The only free parameter in the PFSS model is the radius of the so-called source surface, where magnetic field lines are forced to open. The radius of this surface is typically set to 2.5 solar radii in research and operational PFSS numerical models. Here, using Global Oscillation Network Group (GONG) synoptic maps of the photospheric field, solutions of the PFSS model for various heights of the source surface are investigated for 2006-2018. In particular, numerically derived open solar magnetic flux and coronal holes are examined. Solutions of the PFSS model based on GONG synoptic maps are particularly important since they are often used to drive operational space weather forecast models. Comparisons between observations and numerical results in this paper suggest that the radius of the source surface is significantly lower than 2.5 solar radii during the active phase of solar cycle 24. The fact that the source surface location depends on the solar activity suggests that relations which associate solar wind properties with the coronal magnetic field in the PFSS-based solar wind modes should be revisited. Furthermore, although the correction of the polar magnetic field is part of GONG synoptic map production pipeline, the results suggest that better treatment of polar fields is needed to cover observational gaps. The issue with the polar fields in GONG maps is particularly pronounced in recent years.

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Section: Resultsmentioning

confidence: 99%

On Solutions of the PFSS Model With GONG Synoptic Maps for 2006–2018

Nikolić

2019

Space Weather

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“…Examples include the potential field source surface model (PFSS; Altschuler and Newkirk, 1969), its improved version including the Schatten current sheet, the Wang-Sheeley-Arge model (WSA model; Arge and Pizzo, 2000) and the MULTI-VP model (Pinto and Rouillard, 2017). Studies comparing the two different conceptual approaches have shown significant differences in the size, location, shape and occurrence of the dark and/or open structures defined as CHs (e.g., Lowder et al, 2014;Lowder, Qiu, and Leamon, 2017;Linker et al, 2017;Wallace et al, 2019;Huang, Lin, and Lee, 2019;Asvestari et al, 2019). Additionally new approaches like machine learning/neural networks (e.g., Illarionov and Tlatov, 2018) and extraction methods based on plasma properties (differential emission measure; Raymond and Doyle, 1981;Hahn, Landi, and Savin, 2011) are the topic of current research.…”

Section: Introductionmentioning

confidence: 99%

Statistical Analysis and Catalog of Non-polar Coronal Holes Covering the SDO-Era Using CATCH

et al. 2019

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Coronal holes are usually defined as dark structures seen in the extreme ultraviolet and X-ray spectrum which are generally associated with open magnetic fields. Deriving reliably the coronal hole boundary is of high interest, as its area, underlying magnetic field, and other properties give important hints as regards high speed solar wind acceleration processes and compression regions arriving at Earth. In this study we present a new threshold-based extraction method, which incorporates the intensity gradient along the coronal hole boundary, which is implemented as a user-friendly SSW-IDL GUI. The Collection of Analysis Tools for Coronal Holes (CATCH) enables the user to download data, perform guided coronal hole extraction and analyze the underlying photospheric magnetic field. We use CATCH to analyze non-polar coronal holes during the SDO-era, based on 193 Å filtergrams taken by the Atmospheric Imaging Assembly (AIA) and magnetograms taken by the Heliospheric and Magnetic Imager (HMI), both on board the Solar Dynamics Observatory (SDO). Between 2010 and 2019 we investigate 707 coronal holes that are located close to the central meridian. We find coronal holes distributed across latitudes of about ± 60 • , for which we derive sizes between 1.6 × 10 9 and 1.8 × 10 11 km 2. The absolute value of the mean signed magnetic field strength tends towards an average of 2.9 ± 1.9 G. As far as the abundance and size of coronal holes is concerned, we find no distinct trend towards the northern or southern hemisphere. We find that variations in local and global conditions may significantly change Electronic supplementary material The online version of this article (

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“…As already discussed in other works (e.g., Arden et al, ; Linker et al, ; Wallace et al, ), discrepancies exist between in situ measured at 1 AU and model computed open flux using the PFSS model, and subsequently the WSA model. Considering the standard paradigm that CHs are primary sources of open flux (Linker et al, ; Mackay & Yeates, ), testing whether CHs are properly modeled is a logical step.…”

Section: Conclusion and Discussionmentioning

confidence: 63%

“…It is noteworthy that this result is based on analyzing a CH sample from only one solar cycle and considers CHs located in the central meridional zone. Increasing the size of the sample and also extending it over a larger period of time can potentially lead to different height selection.Although following different techniquesLowder et al (2014),Linker et al (2017), andWallace et al (2019) overplotted automatically detected CHs on synoptic magnetic maps but still resulted in underestimated open flux, according toLinker et al (2017), the result could only be improved by considering areas larger than the detected CHs, leading them to the conclusion that either synoptic maps underestimate the solar magnetic flux or that CHs are not the sole source of open flux. In addition, there are studies that challenge the certainty that the open flux from in situ measurements should be an exact match to that modelled close to the Sun, arguing that there might be other processes/factors affecting it, as suggested, for example, inLockwood et al (2009), where they found that the excess open flux between models and in situ measurements can be explained by kinematic effects of variations of the SW speed.…”

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confidence: 99%

Reconstructing Coronal Hole Areas With EUHFORIA and Adapted WSA Model: Optimizing the Model Parameters

et al. 2019

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The adopted Wang-Sheeley-Arge (WSA) model embedded in EUHFORIA (EUropean Heliospheric FORecasting Information Asset) is compared to EUV observations. According to the standard paradigm, coronal holes are sources of open flux; thus, we use remote sensing EUV observations and catch (Collection of Analysis Tools for Coronal Holes) to extract CH areas and compare them to the open flux areas modeled by EUHFORIA. From the adopted WSA model we employ only the Potential Field Source Surface (PFSS) model for the inner corona and the Schatten Current Sheet (SCS) model for the outer (PFSS+SCS). The height, R ss , of the outer boundary of the PFSS, known as the source surface, and the height, R i , of the inner boundary of the SCS are important parameters affecting the modeled CH areas.We investigate the impact the two model parameters can have in the modeled results. We vary R ss within the interval [1.4, 3.2]R ⊙ with a step of 0.1R ⊙ , and R i within the interval [1.3, 2.8]R ⊙ with the same step, and the condition that R i < R ss . This way we have a set of 184 initial parameters to the model, and we assess the model results for all these possible height pairs. We conclude that the default heights used so far fail in modeling accurately CH areas and lower heights need to be considered.

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Estimating Total Open Heliospheric Magnetic Flux

Cited by 61 publications

References 58 publications

On Solutions of the PFSS Model With GONG Synoptic Maps for 2006–2018

On Solutions of the PFSS Model With GONG Synoptic Maps for 2006–2018

Statistical Analysis and Catalog of Non-polar Coronal Holes Covering the SDO-Era Using CATCH

Reconstructing Coronal Hole Areas With EUHFORIA and Adapted WSA Model: Optimizing the Model Parameters

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