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| Paper: |
Multitaper Spectral Analysis and Wavelet Denoising Applied to Helioseismic Data |
| Volume: |
154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop |
| Page: |
783 |
| Authors: |
Komm, Rudolf; Gu, Yeming; Hill, Frank; Stark, Phil; Fodor, Imola |
| Abstract: |
Our goal is to improve the estimates of mode frequencies, amplitudes, and widths derived from helioseismic observations. To this end, we apply Multitaper Spectral Analysis (MTSA) to the observed time series to derive power spectrum estimates, and then we apply wavelet denoising to the log spectra to further improve the signal-to-noise ratio of the modes. The rationale behind this approach is that MTSA leads to a power spectrum estimate with reduced variance and better leakage properties than the conventional periodogram and that since the log multitaper spectrum is close to Gaussian, distributed wavelet denoising is the optimum method to reduce the noise level in the calculated spectra. We applied MTSA and wavelet denoising to GONG and SOHO-SOI/MDI time series and found that a single m-nu spectrum benefits greatly from MTSA plus wavelet denoising and that wavelet denoising by itself can be used to improve m-averaged spectra. |
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