3-Phase Evolution of a Coronal Hole, Part II: The Magnetic Field

Abstract

We investigate the magnetic characteristics of a persistent coronal hole (CH) extracted from EUV imagery using HMI filtergrams over the timerange February 2012-October 2012. The magnetic field, its distribution as well as the magnetic fine structure in form of flux tubes (FT) are analyzed in different evolutionary states of the CH. We find a strong linear correlation between the magnetic properties (e.g. signed/unsigned magnetic field strength) and area of the CH. As such, the evolutionary pattern in the magnetic field clearly follows the three-phase evolution (growing, maximum and decaying phase) as found from EUV data (Part I). This evolutionary process is most likely driven by strong FTs with a mean magnetic field strength exceeding 50 G. During the maximum phase they entail up to 72% of the total signed magnetic flux of the CH, but only cover up to 3.9% of the total CH area, whereas during the growing and decaying phase, strong FTs entail 54-60% of the signed magnetic flux and cover around 1-2% of the CHs total area. We conclude that small scale-structures of strong unipolar magnetic field are the fundamental building blocks of a CH and govern its evolution.

under revision for ApJ

References in corpus (13)

• The Magnetic Field in the Solar Atmosphere
• Observables Processing for the Helioseismic and Magnetic Imager Instrument on the Solar Dynamics Observatory
• Strong horizontal photospheric magnetic field in a surface dynamo simulation
• Automated Coronal Hole Detection using Local Intensity Thresholding Techniques
• The Solar Internetwork. I. Contribution to the Network Magnetic Flux
• Turbulent small-scale dynamo action in solar surface simulations
• A multiple flux-tube solar wind model
• 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
• Links between magnetic fields and plasma flows in a coronal hole
• 3-Phase Evolution of a Coronal Hole, Part I: 360° remote sensing and in-situ observations
• Turbulence-Driven Coronal Heating and Improvements to Empirical Forecasting of the Solar Wind
• Coronal Hole and Solar Global Magnetic Field Evolution in 1976-2012

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