A&A 396, 243-253 (2002)
DOI: 10.1051/0004-6361:20021358

Detectability of large-scale flows in global helioseismic data - A numerical experiment

M. Roth¹, R. Howe² and R. Komm<sup>2

1</sup>  Kiepenheuer-Institut für Sonnenphysik, 79104 Freiburg, Germany
²  National Solar Observatory (Operated by the Association of Universities for Research in Astronomy, Inc. under cooperative agreement with the National Science Foundation.) , 950 N. Cherry Ave., Tucson, AZ 85719, USA

(Received 5 November 2001 / Accepted 18 September 2002 )

Abstract
Convective motions affect the solar p-modes by shifting their frequencies. In comparison to the frequency splitting caused by the differential rotation, this is only a small additional effect. As the spatial resolution of the inversions for the differential rotation becomes better, it is important to know how these additional frequency shifts modify the splitting coefficients and how these two effects might be disentangled. Therefore we carry out a numerical experiment. We use quasi-degenerate perturbation theory to create frequencies of p-modes that are affected by differential rotation and by large-scale flows. The simulated frequency sets are analyzed and inverted for differential rotation. We use changes in the coverage, the multiplets, and the inversion results as diagnostics to draw conclusions about the detectability of large-scale flows in global helioseismic data. The result is a detectability limit of the order of 10 m s ^-1 for large-scale flows in the convection zone. A sectoral poloidal flow with greater amplitude will lead to a noticeable distortion of the rotation rate, while a zonal poloidal flow with greater amplitude will lead to distorted even- a coefficients and disrupted multiplets.

Key words: convection -- Sun: rotation -- Sun: oscillations

Offprint request: M. Roth, mroth@kis.uni-freiburg.de

© ESO 2002