EDP Sciences
Free access
Volume 379, Number 3, December I 2001
Page(s) 1039 - 1044
Section The Sun
DOI http://dx.doi.org/10.1051/0004-6361:20011254
A&A 379, 1039-1044 (2001)
DOI: 10.1051/0004-6361:20011254

Noise reduction in helioseismic power spectra by non-orthogonal wavelets

S. K. Solanki1, C. Régulo2, 3, M. Fligge4 and A. G. Kosovichev5

1  Max-Planck-Institut für Aeronomie, 37191 Katlenburg-Lindau, Germany
2  Instituto de Astrofisica de Canarias, 38205 La Laguna, Tenerife, Spain
3  Departamento de Astrofisica de la Universidad de La Laguna, 38206 Tenerife, Spain
4  Institute of Astronomy, ETH-Zentrum, 8092 Zürich, Switzerland
5  W. W. Hansen Experimental Physics Laboratory, Stanford University, USA

(Received 19 June 2001 / Accepted 4 September 2001)

We present a method to reduce noise in helioseismic power spectra using a non-orthogonal wavelet transform based on quadratic spline functions. The quality of our method is tested by applying it to artificially generated time-series approximating solar p-modes. The mode frequencies and line widths obtained from least-squares fits to the smoothed spectra are compared with the corresponding parameters deduced from maximum likelihood fits to the original spectra. The results from both approaches are very similar and suggest that there is no major bias in either of these rather independent approaches. As a practical example we denoise parts of the power spectrum obtained from the two first years of operation of the GOLF instrument onboard SOHO.

Key words: methods: data analysis -- methods: statistical -- Sun: oscillations

Offprint request: S. K. Solanki, solanki@linmpi.mpg.de

© ESO 2001