Subsurface supergranular vertical flows as measured using large distance separations in time-distance helioseismology

T. L. Duvall, Shravan Hanasoge

Research output: Chapter in Book/Report/Conference proceedingChapter

Abstract

As large-distance rays approach the solar surface approximately vertically, travel times measured from surface pairs for these large separations are mostly sensitive to vertical flows, at least for shallow flows within a few Mm of the solar surface. All previous analyses of supergranulation have used smaller separations and have been hampered by the difficulty of separating the horizontal and vertical flow components. We find that the large-separation travel times associated with supergranulation cannot be studied using the standard phase-speed filters of time-distance helioseismology. These filters, whose use is based upon a refractive model of the perturbations, reduce the resultant traveltime signal by at least an order of magnitude at some distances. More effective filters are erived. Modeling suggests that the center-annulus travel-time difference in the separation range is insensitive to the horizontally diverging flow from the centers of the supergranules and should lead to a constant signal from the vertical flow. Our measurement of this quantity, seconds, is constant over the distance range. This magnitude of the signal cannot be caused by the level of upflow at cell centers seen at the photosphere of extended in depth. It requires the vertical flow to increase with depth. A simple Gaussian model of the increase with depth implies a peak upward flow of at a depth of 2.3 Mm and a peak horizontal flow of at a depth of 1.6 Mm.

Original languageEnglish (US)
Title of host publicationSolar Dynamics and Magnetism from the Interior to the Atmosphere
PublisherSpringer New York
Pages71-83
Number of pages13
ISBN (Electronic)9781489980052
ISBN (Print)9781489980045
DOIs
StatePublished - Jan 1 2014

Fingerprint

helioseismology
travel
filters
annuli
photosphere
rays
perturbation
cells

Keywords

  • Helioseismology, direct modeling
  • Helioseismology, observations
  • Interior, convective zone
  • Supergranulation
  • Velocity fields, interior

ASJC Scopus subject areas

  • Physics and Astronomy(all)

Cite this

Duvall, T. L., & Hanasoge, S. (2014). Subsurface supergranular vertical flows as measured using large distance separations in time-distance helioseismology. In Solar Dynamics and Magnetism from the Interior to the Atmosphere (pp. 71-83). Springer New York. https://doi.org/10.1007/978-1-4899-8005-2_5

Subsurface supergranular vertical flows as measured using large distance separations in time-distance helioseismology. / Duvall, T. L.; Hanasoge, Shravan.

Solar Dynamics and Magnetism from the Interior to the Atmosphere. Springer New York, 2014. p. 71-83.

Research output: Chapter in Book/Report/Conference proceedingChapter

Duvall, TL & Hanasoge, S 2014, Subsurface supergranular vertical flows as measured using large distance separations in time-distance helioseismology. in Solar Dynamics and Magnetism from the Interior to the Atmosphere. Springer New York, pp. 71-83. https://doi.org/10.1007/978-1-4899-8005-2_5
Duvall TL, Hanasoge S. Subsurface supergranular vertical flows as measured using large distance separations in time-distance helioseismology. In Solar Dynamics and Magnetism from the Interior to the Atmosphere. Springer New York. 2014. p. 71-83 https://doi.org/10.1007/978-1-4899-8005-2_5
Duvall, T. L. ; Hanasoge, Shravan. / Subsurface supergranular vertical flows as measured using large distance separations in time-distance helioseismology. Solar Dynamics and Magnetism from the Interior to the Atmosphere. Springer New York, 2014. pp. 71-83
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