Anisotropy of the solar network magnetic field around the average supergranule

Abstract

Supergranules in the quiet Sun are outlined by a web-like structure of enhanced magnetic field strength, the so-called magnetic network. We aim to map the magnetic network field around the average supergranule near disk center. We use observations of the line-of-sight component of the magnetic field from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO). The average supergranule is constructed by coaligning and averaging over 3000 individual supergranules. We determine the positions of the supergranules with an image segmentation algorithm that we apply on maps of the horizontal flow divergence measured using time-distance helioseismology. In the center of the average supergranule the magnetic (intranetwork) field is weaker by about 2.2 Gauss than the background value (3.5 Gauss), whereas it is enhanced in the surrounding ring of horizontal inflows (by about 0.6 Gauss on average). We find that this network field is significantly stronger west (prograde) of the average supergranule than in the east (by about 0.3 Gauss). With time-distance helioseismology, we find a similar anisotropy. The observed anisotropy of the magnetic field adds to the mysterious dynamical properties of solar supergranulation.

arXiv comment4 pages, 4 figures, accepted for publication in A&A Letters

References in corpus (3)

• Solar supergranulation as a wavelike phenomenon
• Spatially resolved vertical vorticity in solar supergranulation using helioseismology and local correlation tracking
• Time-distance helioseismology: A new averaging scheme for measuring flow vorticity

Cited by in corpus (7)

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• Evolution and wave-like properties of the average solar supergranule
• Chromospheric observations and magnetic configuration of a supergranular structure
• Intensity contrast of the average supergranule
• Iterative inversion of synthetic travel times successful at recovering sub-surface profiles of supergranular flows
• Texture of average solar photospheric flows and the donut-like pattern
• Validating time-distance helioseismic inversions for non-separable subsurface profiles of an average supergranule