Systematic center-to-LIMB variation in measured helioseismic travel times and its effect on inferences of solar interior meridional flows

Junwei Zhao, Kaori Nagashima, R. S. Bogart, A. G. Kosovichev, T. L. Duvall

Research output: Contribution to journalArticlepeer-review

63 Scopus citations

Abstract

We report on a systematic center-to-limb variation in measured helioseismic travel times, which must be taken into account for an accurate determination of solar interior meridional flows. The systematic variation, found in time-distance helioseismology analysis using SDO/HMI and SDO/AIA observations, is different in both travel-time magnitude and variation trend for different observables. It is not clear what causes this systematic effect. Subtracting the longitude-dependent east-west travel times, obtained along the equatorial area, from the latitude-dependent north-south travel times, obtained along the central meridian area, gives remarkably similar results for different observables. We suggest this as an effective procedure for removing the systematic center-to-limb variation. The subsurface meridional flows obtained from inversion of the corrected travel times are approximately 10ms-1 slower than those obtained without removing the systematic effect. The detected center-to-limb variation may have important implications in the derivation of meridional flows in the deep interior and needs to be better understood.

Original languageEnglish (US)
Article numberL5
JournalAstrophysical Journal Letters
Volume749
Issue number1
DOIs
StatePublished - Apr 10 2012
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

Keywords

  • Sun: helioseismology
  • Sun: interior
  • Sun: oscillations

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