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Session 19 - The Sun.
Oral session, Monday, June 08

[19.01] Initial High-Degree p-Mode Frequencies and Rotational Frequency Splittings from the SOHO SOI/MDI Experiment

E. J. Rhodes Jr. (Univ. Southern Calif./JPL), J. Reiter (Tech. Univ. Munich), A. G. Kosovichev, J. Schou, P. H. Scherrer (Stanford. Univ.)

We present the first high-degree p-mode frequencies and rotationally-induced frequency splittings obtained from the Full-Disk Program of the SOHO Solar Oscillation Investigation/Michelson Doppler Imager experiment. The frequencies and splittings which we present here were computed from power spectra obtained during the 1996 SOI/MDI Dynamics Run. Specifically, a 60.75-day time series of full-disk Dopplergrams was converted into sets of zonal, tesseral, and sectoral power spectra covering the degree range of 0 through 1000. Estimates of the n-averaged frequency splittings were computed for the frequency range of 1800 to 4800 microhertz at each degree and these averaged splitting coefficients were then employed to compute an average power spectrum for that degree. From these 1001 average power spectra estimates were made of the frequencies, frequency uncertainties, widths, peak power densities, and background power densities of a total of 13664 separate peaks in the set of 1001 average power spectra. A total of 2554 of these peaks were isolated enough in their respective spectra to be fit as single p-modes. However, for the remaining 11110 peaks (mostly those above \l=200), the individual p-mode peaks and their spatial sidelobes were located so close together in frequency that they appeared as ridges rather than as isolated modal peaks in the average power spectra. For these p-mode ridges we obtained so-called ``ridge-fit'' parameter estimates. Observed asymmetries in the p-mode ridge shapes altered the fitted peak frequencies from their ``true'' values and required that we correct the raw ridge-fit frequencies.

Forty sets of these power spectra were also processed to yield estimates of the rotational splitting coefficients for individual p-mode ridges for every 25th degree between \l=25 and 1000. For \l between 25 and 175 we will compare these Full-Disk program splittings with the previously-published splittings from the 1996 SOI/MDI Medium-\l Program (Kosovichev et al., Solar Physics, 170, 43-61,1997).

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