EDP Sciences
Free access
Volume 438, Number 3, August II 2005
Page(s) 1083 - 1097
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20052695

A&A 438, 1083-1097 (2005)
DOI: 10.1051/0004-6361:20052695

On the effect of the inhomogeneous subsurface flows on the high degree solar p-modes

B. M. Shergelashvili and S. Poedts

Centre for Plasma Astrophysics, Katholieke Universiteit Leuven, Celestijnenlaan 200B, 3001 Leuven, Belgium
    e-mail: [Bidzina.Shergelashvili;Stefaan.Poedts]@wis.kuleuven.ac.be

(Received 28 May 2002 / Accepted 5 April 2005)

The observed power spectrum of high-degree solar p-modes ($\ell>200$) shows discrepancies with the power spectrum predicted by the stochastic excitement and damping theory. In an attempt to explain these discrepancies, the present paper is concerned with the influence of the observed subsurface flows on the trapped acoustic modes (p-modes). The effect of these inhomogeneous background flows is investigated by means of a non-modal analysis and a multi-layer model. It is shown that the rotational and meridional components of the velocity field change the wavelengths of the oscillation modes which, in turn, results in modifications of the corresponding modal frequencies. The magnitudes of the frequency residuals depend on the spatial scales of the modes and on the gradients of the different components of the flow velocity. Together with other mechanisms (e.g. the scattering of modes by the large-scale convection), the non-modal effect of the variation of the frequencies in time may contribute: 1) to the observed widening of the corresponding peaks in the observed power spectrum with increasing angular degree; 2) to the partial dissipation of spectral power, and, as a result; 3) to the discrepancies between the predicted and the observed power spectrum of solar p-modes.

Key words: Sun: oscillations -- Sun: rotation -- hydrodynamics -- waves

© ESO 2005