New Evidence that Magnetoconvection Drives Solar-Stellar Coronal Heating

Abstract

How magnetic energy is injected and released in the solar corona, keeping it heated to several million degrees, remains elusive. Coronal heating generally increases with increasing magnetic field strength. From comparison of a non-linear force-free model of the three-dimensional active-region coronal field to observed extreme-ultraviolet loops, we find that (1) umbra-to-umbra coronal loops, despite being rooted in the strongest magnetic flux, are invisible, and (2) the brightest loops have one foot in an umbra or penumbra and the other foot in another sunspot's penumbra or in unipolar or mixed-polarity plage. The invisibility of umbra-to-umbra loops is new evidence that magnetoconvection drives solar-stellar coronal heating: evidently the strong umbral field at \underline{both} ends quenches the magnetoconvection and hence the heating. Broadly, our results indicate that, depending on the field strength in both feet, the photospheric feet of a coronal loop on any convective star can either engender or quench coronal heating in the loop's body.

13 pages, 5 figures, to appear in ApJ Letters, movies temporarily available at: https://www.dropbox.com/sh/pysbv0o92jlshew/AACa-d8xjrF1sdSt7Yh9msHoa?dl=0

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• The Magnetic Field in the Solar Atmosphere
• Solar Coronal Loops Associated with Small-scale Mixed Polarity Surface Magnetic Fields
• Trigger Mechanism of Solar Subflares in a Braided Coronal Magnetic Structure

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• The Magnetic Properties of Heating Events on High-Temperature Active Region Loops
• Signatures of ubiquitous magnetic reconnection in the deep atmosphere of sunspot penumbrae
• Magnetic filed dynamics and varying plasma emission in large coronal loops
• Prospective Implications of EUV Coronal Plumes for Magnetic-network Genesis of Coronal Heating, Coronal-hole Solar Wind, and Solar-wind Magnetic-field Switchbacks
• Are the brightest coronal loops always rooted in mixed-polarity magnetic flux?
• Case study on the identification and classification of small-scale flow patterns in flaring active region