Issue |
A&A
Volume 438, Number 3, August II 2005
|
|
---|---|---|
Page(s) | 1083 - 1097 | |
Section | The Sun | |
DOI | https://doi.org/10.1051/0004-6361:20052695 | |
Published online | 18 July 2005 |
On the effect of the inhomogeneous subsurface flows on the high degree solar p-modes
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 () 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
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