SYSTEMATIC CENTER-TO-LIMB VARIATION IN MEASURED HELIOSEISMIC TRAVEL TIMES AND ITS EFFECT ON INFERENCES OF SOLAR INTERIOR MERIDIONAL FLOWS

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 observation...

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Bibliographic Details
Published inAstrophysical journal. Letters Vol. 749; no. 1; pp. 1 - 6
Main Authors Zhao, Junwei, Nagashima, Kaori, Bogart, R S, Kosovichev, A G, DUVALL, T L
Format Journal Article
LanguageEnglish
Published United States 10.04.2012
Subjects
ASTRONOMY
ASTROPHYSICS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Derivation
DISTANCE
Equatorial regions
Helioseismology
Inversions
Meridional flow
OSCILLATIONS
SEISMICITY
SOLAR ACTIVITY
Solar interior
SUN
Trends
VARIATIONS
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Summary: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 10 m s super(-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.
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ISSN:2041-8205
2041-8213
DOI:10.1088/2041-8205/749/1/L5