Automated identification of coronal holes from synoptic EUV maps

Abstract

Coronal holes (CH) are regions of open magnetic field lines in the solar corona and the source of fast solar wind. Understanding the evolution of coronal holes is critical for solar magnetism as well as for accurate space weather forecasts. We study here the extreme ultraviolet (EUV) synoptic maps at three wavelengths (195A/193A, 171A and 304A) measured by Solar and Heliospheric Observatory/Extreme Ultraviolet Imaging Telescope (SOHO/EIT) and Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) instruments. The two datasets are first homogenized by scaling the SDO/AIA data to the SOHO/EIT level by means of histogram equalization. We then develop a novel automated method to identify CHs from these homogenized maps by determining the intensity threshold of CH regions separately for each synoptic map. This is done by identifying the best location and size of an image segment, which optimally contains portions of coronal holes and the surrounding quiet Sun allowing us to detect the momentary intensity threshold. Our method is thus able to adjust itself to the changing scale size of coronal holes and to temporally varying intensities. To make full use of the information in the three wavelengths we construct, a composite CH distribution, which is more robust than distributions based on one wavelength. Using the composite CH dataset we discuss the temporal evolution of CHs during the solar cycles 23 and 24.

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Cited by in corpus (12)

• Statistical Analysis and Catalog of Non-polar Coronal Holes Covering the SDO-era using CATCH
• Estimating Total Open Heliospheric Magnetic Flux
• Multi-channel coronal hole detection with convolutional neural networks
• The Observational Uncertainty of Coronal Hole Boundaries in Automated Detection Schemes
• New Homogeneous Dataset of Solar EUV synoptic maps from SOHO/EIT and SDO/AIA
• Machine-learning approach to identification of coronal holes in solar disk images and synoptic maps
• Quantifying the Consistency and Characterizing the Confidence of Coronal Holes Detected by Active Contours without Edges (ACWE)
• SIP-IFVM: Efficient time-accurate magnetohydrodynamic model of the corona and coronal mass ejections
• The Missing Cool Corona in the Flat Magnetic Field around Solar Active Regions
• Time-evolving coronal modelling of the solar maximum around the solar storms in May 2024 by COCONUT
• Characteristics of ephemeral coronal holes
• Magnetic Field-Constrained Ensemble Image Segmentation of Coronal Holes in Chromospheric Observations