Photospheric magnetic structure of coronal holes

Abstract

In this study, we investigate in detail the photospheric magnetic structure of 98 coronal holes using line-of-sight magnetograms of SDO/HMI, and for a subset of 42 coronal holes using HINODE/SOT G-band filtergrams. We divided the magnetic field maps into magnetic elements and quiet coronal hole regions by applying a threshold at $\pm 25$ G. We find that the number of magnetic bright points in magnetic elements is well correlated with the area of the magnetic elements (cc=$0.83\pm 0.01$). Further, the magnetic flux of the individual magnetic elements inside coronal holes is related to their area by a power law with an exponent of $1.261\pm 0.004$ (cc=$0.984\pm 0.001$). Relating the magnetic elements to the overall structure of coronal holes, we find that on average ($69\pm 8$) % of the overall unbalanced magnetic flux of the coronal holes arises from long-lived magnetic elements with lifetimes > 40 hours. About ($22\pm 4$) % of the unbalanced magnetic flux arises from a very weak background magnetic field in the quiet coronal hole regions with a mean magnetic field density of about 0.2 to 1.2 G. This background magnetic field is correlated to the flux of the magnetic elements with lifetimes of > 40 h (cc=$0.88\pm 0.02$). The remaining flux arises from magnetic elements with lifetimes < 40 hours. By relating the properties of the magnetic elements to the overall properties of the coronal holes, we find that the unbalanced magnetic flux of the coronal holes is completely determined by the total area that the long-lived magnetic elements cover (cc=$0.994\pm 0.001$).

References in corpus (4)

• The Solar Optical Telescope for the Hinode Mission: An Overview
• Similarities and Differences between Coronal Holes and the Quiet Sun: Are Loop Statistics the Key?
• Characteristics of Low-Latitude Coronal Holes near the Maximum of Solar cycle 24
• Temporal relations between magnetic bright points and the solar sunspot cycle

Cited by in corpus (20)

• The Sun and Space Weather
• Multi-channel coronal hole detection with convolutional neural networks
• Differential Emission Measure Plasma Diagnostics of a Long-Lived Coronal Hole
• The Observational Uncertainty of Coronal Hole Boundaries in Automated Detection Schemes
• Stirring the Base of the Solar Wind: On Heat Transfer and Vortex Formation
• A Universal Method for Solar Filament Detection from H-alpha Observations using Semi-supervised Deep Learning
• Could switchbacks originate in the lower solar atmosphere? I. Formation mechanisms of switchbacks
• How to Estimate the Far-Side Open Flux using STEREO Coronal Holes
• Characteristics of Chromospheric Oscillation Periods in Magnetic Bright Points (MBPs)
• A comparative study of resistivity models for simulations of magnetic reconnection in the solar atmosphere. II. Plasmoid formation
• Solar Polar Flux Redistribution based on Observed Coronal Holes
• Extreme-ultraviolet (EUV) observables of simulated plasmoid-mediated reconnection in the solar corona
• Differences in physical properties of coronal bright points and their ALMA counterparts within and outside coronal holes
• On the short term stability and tilting motion of a well-observed low-latitude solar coronal hole
• Magnetic Flux Emergence in a Coronal Hole
• Magnetic Field-Constrained Ensemble Image Segmentation of Coronal Holes in Chromospheric Observations
• Existence of The Closed Magnetic Field Lines Crossing The Coronal Hole Boundaries
• Earth-affecting Solar Transients: A Review of Progresses in Solar Cycle 24
• Early Evolution of Earth-Directed Coronal Mass Ejections in the Vicinity of Coronal Holes
• Statistical Analysis of Minifilament Eruptions Using Full-disk H$\alpha$ Blue-wing Observations at Big Bear Solar Observatory