Signal-to-noise enhancement in ground-based intensity observations of solar P modes

Details Signal-to-noise enhancement in ground-based intensity observations of solar P modes Signal-to-noise enhancement in ground-based intensity observations of solar P modes

Mar 1995

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995soph..157...17g&link_type=abstract

Solar Physics (ISSN 0038-0938), vol. 157, no. 1-2, p. 17-29

Physics

Luminous Intensity, Modes, P Band, Signal To Noise Ratios, Solar Physics, Space Observations (From Earth), Sun, Wave Propagation, Atmospherics, Noise Spectra, Photosphere, Power Spectra, Solar Cycles

Scientific paper

Intensity observations of solar p modes are needed to form a complete picture of wave propagation in the photosphere. Ground-based intensity observations are severely hampered by terrestrial atmospheric noise. Partial cancellation of the noise power can be achieved if two spectra having disparate signal-to- noise ratios, and based on time series acquired simultaneously at the same site, are combined. A method of combining the spectra is suggested in which one amplitude is scaled and subtracted from the other. The result is squared yielding a positive-definite power density. To test the method, the intensity of light scattered by the Earth's atmosphere was recorded at fifteen- second intervals in two narrow bands centered on 0.5 microns and 1.6 microns. When the two resulting spectra were combined, the noise power was attenuated by a factor of 2.7. The scale factor was varied about its optimum value, revealing that noise peaks have a different signature than signal peaks, and opening up the possibility of a new tool in discrimination against noise peaks. Maxima at symmetry-allowed frequencies and minima at symmetry- forbidden frequencies indicate that the possibility that these results are obtained by chance is only 6.1 x 10-4. The positions of these maxima and minima also support the solar-cycle dependent frequency shifts found by Palle, Regulo, and Roca Cortes.

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