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Astron. Astrophys. 333, 362-368 (1998)


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Power spectrum modelisation of helioseismic data: an application to the measurement of solar p-mode uncertainties

D. Fierry Fraillon 1, B. Gelly 1, F.X. Schmider 1, F. Hill 2, E. Fossat 1 and A. Pantel 1

1 Département d'Astrophysique, C.N.R.S. UMR 6525, Université des Sciences, F-06108 Nice Cedex 2, France
2 National Solar Observatory / N.O.A.O., P.O. Box 26732, Tucson, AZ 85726, USA

Received 5 November 1997 / Accepted 19 December 1997

Abstract

We estimate the statistical uncertainties of low-l solar p-modes parameters based on a Monte Carlo approach. Random perturbations of ideal Lorentz profiles [FORMULA] can provide many estimations of the set of p-modes parameters [FORMULA] and allow one to estimate statistical error-bars [FORMULA] by modelling the parameters' distribution function. Unlike frequencies, which show symmetric distributions, amplitudes and linewidths have asymmetric probability density function similar to the distribution function for time-averaged energies of stochastically excited solar p-modes (Kumar, 1988). A comparison between [FORMULA] and uncertainties based on Hessian's computation (Libbrecht 1992, Toutain and Appourchaux 1994) shows a nice agreement. However, our error-bars take into account more statistical effects, and rely less on the initial parameters' estimation. Such a technique has been used on the IRIS power spectra computed from gapped data, and on one GONG power spectrum computed from almost continuous data. We also present IRIS linewidths and error bars averaged over the years 1989-92 and computed with a fitting strategy using imposed frequency which improves the value of both the parameter and its uncertainty.

Key words: Sun: oscillations – methods: statistical

Send offprint requests to: fierry@irisalfa.unice.fr

© European Southern Observatory (ESO) 1998

Online publication: April 15, 1998
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