[en] We present results from fitting all the available data to date from the three major helioseismic instruments: MDI, GONG and HMI. These data were fitted using an innovative and independent methodology devised a few years ago. The mode fitting was carried out on time series of varying lengths (1×, 2×, 4×, 8×, 16×, 32×, 64 × 72 day-long), using co-eval epochs for all three data sets. By fitting time series of varying lengths, one trades off some temporal resolution for a better precision. We present a comparison of these results, and discuss the potential sources of the residual small discrepancies. We also present inferences from these results on the determination of the solar internal rotation and changes with epoch and thus activity levels.

[en] We present inferences of the internal solar rotation rate and its evolution during solar cycle 23. A full solar cycle of MDI observations have been analyzed using an improved fitting methodology and using time series of various lengths, up to a single 4,608 day long epoch (64 times 72 days or 12.6 yr). We used time series of spherical harmonic coefficients computed by the MDI group, including those resulting from using their improved spatial decomposition. This decomposition includes our best estimate of the image plate scale and of the MDI instrumental image distortion. The leakage matrix used in the fitting includes the effect of the distortion of the eigenfunctions by the solar differential rotation, while the undistorted leakage matrix was itself carefully reviewed and independently recomputed. Rotation inversions were carried out for all available mode sets, fitted for that epoch, including the MDI and GONG 'pipe-line' values. The improved inversion method uses an iterative methodology based on a least-squares regularization, but with an optimal model grid determined by the actual information in the input set. This method also allows us to use an optimized irregular grid, with a variable number of latitudes at different depths.

[en] One salient result of global helioseismology is the mapping of the so-called torsional oscillations below the solar surface. These subsurface flows are inferred by inverting rotational frequency splitting sets of global modes. These flows extend down to a depth of at least 0.8 R, and are likely associated with the activity cycle of our star. To better understand the mechanisms that drive the solar cycle we need to accurately map these flows, and characterize precisely their penetration depth and their temporal behavior. We present a study of the spatial (depth and latitude) and temporal variations of the solar rotation rate associated with the torsional oscillation based on state-of-the-art mode fitting of time series of various lengths of MDI observations, namely 1456-, 728-, 364- and 182-day long time series. Such approach allows us to better estimate how much significant information can be extracted from the different time spans and hence trade off time resolution for precision in the inverted profiles resulting from the different mode sets.

[en] One of the main drawbacks in the analysis of the dynamics of the solar core comes from the lack of consistent data sets that cover the low and intermediate degree range (l = 1,200). It is usually necessary to merge data obtained from different instruments and/or fitting methodologies and hence one introduces undesired systematic errors. In contrast, we present the results of analyzing MDI rotational splittings derived by a single fitting methodology applied to 4608-, 2304-, etc..., down to 182-day long time series. The direct comparison of these data sets and the analysis of the numerical inversion results have allowed us to constrain the dynamics of the solar core and to establish the accuracy of these data as a function of the length of the time-series.

[en] Since the detection of the asymptotic properties of the dipole gravity modes in the Sun, the quest to find individual gravity modes has continued. An extensive and deeper analysis of 14 years of continuous GOLF/SoHO observational data, unveils the presence of a pattern of peaks that could be interpreted as individual dipole gravity modes in the frequency range between 60 and 140 microHz, with amplitudes compatible with the latest theoretical predictions. By collapsing the power spectrum we have obtained a quite constant splitting for these patterns in comparison to regions where no g modes were expected. Moreover, the same technique applied to simultaneous VIRGO/SoHO data unveils some common signals between the power spectra of both instruments. Thus, we are able to identify and characterize individual g modes with their central frequencies, amplitudes and splittings allowing to do seismic inversions of the rotation profile inside the solar core. These results open a new light on the physics and dynamics of the solar deep core.