Sylvain Gereon Korzennik

What we know about the sun's internal rotation from solar oscillations

In this paper, a uniform approach of inversion was used to determine the internal rotation rate of the sun from each of the six available sets of solar oscillation data, which included the data of Duvall et al. (1986), Rhodes et al. (1987, 1990), Tomczyk (1988), Brown and Morrow (1987), and Libbrecht (1989). The technique chosen for inverting the solar oscillation data was the discretized least-squares technique. The results indicate that the rotation rate of the sun in the equatorial plane declines going inward between the surface and 0.6 of the radius and that the polar rate increases going inward (i.e., the surfacelike differential rotation decreases with depth). 21 refs.

Contribution of high-degree frequency splittings to the inversion of the solar rotation rate

We present the contribution of high degree rotational splittings to the inversion of the internal rotation rate around the equator. The extention of the input data set to l of 500, allow us to improve the resolution of the solution mainly in the outermost 15% of the solar radius. The rotational profile obtained in the regions below the surface leads to an attractive picture that could reconcile different non-seismic estimates of the “surface” rotation rate.

Measurements of intermediate- and high-degree (20 < l <600) p-mode solar oscillation power and energy

We present measurements of the total modal power and energy of both intermediate- and high-degree (20< l <600) solar p-mode oscillations which have been corrected to first order for the combined effects of atmospheric seeing, image motion due to imperfect tracking, and the point spread function of our optics. These power and energy estimates have been obtained from an average of 20 separate zonal l - n power spectra, which were obtained from observations obtained at the 60-Foot Solar Tower of the Mt. Wilson Observatory between July 1 and 20, 1988. The raw total power values were obtained from a least-squares fitting of Lorentzian profiles to the p-mode ridges in the average zonal power spectrum. As an initial method of correcting the observed power levels, we adopted the procedure described by Kaufman (1988) and deconvolved measurements of the observed limb profiles from one of our images using two slightly different theoretical unblurred limb profiles in order to obtain two estimates of the modulation transfer function (mtf) of our experiment. The corrected power values which resulted show systematic variations with both frequency and degree which are similar to those obtained by Kaufman. For example, between l = 100 and 600 our corrected power values drop by a factor of at least 4.5, although the magnitude of our correction becomes less certain as the degree is increased above 300. We also convert these power values into estimates of the total energy of the modes to show that the modal energies decrease by a factor of at least 15 over the same range in l. Even given the uncertainty of our correction at the higher degrees, the consistency of the l-dependent decrease in the modal energies with similar results by Kaufman (1990) suggests that, at least above l = 100, the modes are not in energy equipartition with turbulent convective eddies.

Has the sun's internal rotation changed through this activity cycle ?

The internal rotation of the Sun is determined from each of the six available sets of solar oscillation splitting data. These data span this activity cycle and best sample the region near the base of the convection zone. Going inwards through the convection zone into the outer radiative interior, the robust results are a decrease in the rotation rate in the equatorial plane and a trend away from the surface-like differential rotation toward solid body rotation. In the equatorial plane of the radiative interior, the rotation rate seems to systematically increase through the solar cycle. If true, this suggests that the interior has a role in the activity cycle.

Solar oscillation ring diagrams from Mt. Wilson full-disk magneto-optical Dopplergrams

Three-dimensional power spectra of solar oscillations have been computed from moderate-resolution full disk Doppler images obtained with the Magneto-Optical Filter at Mt. Wilson. Slices of the spectra at constant frequency reveal the ring structures that are analogous to the ridges in two-dimensional spectra. Ring diagrams obtained at different heliographic positions show large differences in the structure of the rings. These variations can be attributed to the changing effective spatial resolution of the observations across the disk. After correction for this effect, and .for terrestrial seeing, the rings will be used to map the horizontal flows in the convection zone as a function of position and depth.