Solar east-west flow correlations that persist for months at low latitudes are dominated by active region inflows

Abstract

Context: Giant-cell convection is believed to be an important component of solar dynamics. For example, it is expected to play a crucial role in maintaining the Sun's differential rotation. Aims: We re-examine early reports of giant convective cells detected using correlation analysis of Dopplergrams. We extend this analysis using 19 years of space and ground-based observations of near-surface horizontal flows. Method: Flow maps are derived through local correlation tracking of granules and helioseismic ring-diagram analysis. We compute temporal auto-correlation functions of the east-west flows at fixed latitude. Results: Correlations in the east-west velocity can be clearly seen up to five rotation periods. The signal consists of features with longitudinal wavenumbers up to m=9 at low latitudes. Comparison with magnetic images indicates that these flow features are associated with magnetic activity. The signal is not seen above the noise level during solar minimum. Conclusions: Our results show that the long-term correlations in east-west flows at low latitudes are dominantly due to inflows into active regions and not to giant convective cells.

9 pages, 10 figures, accepted into A&A

References in corpus (6)

• Structure and Evolution of Giant Cells in Global Models of Solar Convection
• Helioseismic Imaging of Fast Convective Flows Throughout the Near-Surface Shear Layer
• Evolution of Near-surface Flows Inferred from High-resolution Ring-diagram Analysis
• Helioseismology challenges models of solar convection
• Exploring the latitude and depth dependence of solar Rossby waves using ring-diagram analysis
• Solar Rossby waves observed in GONG++ ring-diagram flow maps

Cited by in corpus (6)

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• Investigating toroidal flows in the Sun using normal-mode coupling