Tri-Phonic Helioseismology: Comparison of Solar p Modes Observed by the Helioseismology Instruments Aboard SOHO

The three helioseismology instruments aboard SOHO observe solar p modes in velocity (GOLF and MDI) and in intensity (VIRGO and MDI). Time series of two months duration are compared and confirm that the instruments indeed observe the same Sun to a high degree of precision. Power spectra of 108 days a...

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Bibliographic Details
Published in:Solar physics 1997-10, Vol.175 (2), p.311-328
Main Authors: Toutain, T, Appourchaux, T, Baudin, F, Fröhlich, C, Gabriel, A, Scherrer, P, Andersen, B N, Bogart, R, Bush, R, Finsterle, W, García, R A, Grec, G, Henney, C J, Hoeksema, J T, Jiménez, A, Kosovichev, A, Roca Cortés, T, Turck-chièze, S, Ulrich, R, Wehrli, C
Format: Article
Language:English
Subjects:
Solar physics
Studies
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Summary:The three helioseismology instruments aboard SOHO observe solar p modes in velocity (GOLF and MDI) and in intensity (VIRGO and MDI). Time series of two months duration are compared and confirm that the instruments indeed observe the same Sun to a high degree of precision. Power spectra of 108 days are compared showing systematic differences between mode frequencies measured in intensity and in velocity. Data coverage exceeds 97% for all the instruments during this interval. The weighted mean differences (V-I) are -0.1 kHz for l=0, and -0.16 kHz for l=1. The source of this systematic difference may be due to an asymmetry effect that is stronger for modes seen in intensity. Wavelet analysis is also used to compare the shape of the forcing functions. In these data sets nearly all of the variations in mode amplitude are of solar origin. Some implications for structure inversions are discussed.
ISSN:0038-0938
1573-093X
DOI:10.1023/A:1004949832159