The rotation of the solar core is an important open question that can be addressed by using spatial data from SOHO. In particular, GOLF experiment is dedicated to the observation of low-degree oscillations which sound the core. Here we use the GOLF frequency splittings [poster 1.39, these proceedings1998] obtained from one year of observation beginning on April 11th 1996 together with the MDI 144-day splittings for degree up to l=250 [Schou et al.1998]. For comparison we have also used the GONG splittings of low-degree modes obtained [Rabello-Soares & Appourchaux1998] from 1 year of ground-based observations (August 1995- August 1996).
Figure 1: Sideral sectoral splittings (GOLF) and 
coefficients (MDI and GONG) with their formal errors as a function of the
turning points of the modes.
Figure 1 shows the GOLF sectoral splittings
with their formal errors whereas for MDI and GONG data the figure shows
the 
coefficients
of the expansion of the splittings on [Ritzwoller
& Lavely1991] polynomials. These two quantities (sectoral splittings
and coefficients)
may differ slightly in theory for l>1 because of the latitudinal
dependence of the solar rotation. In Section 2
we briefly recall how the 2D inverse problem related to the internal rotation
can be reduced to a 1D problem for either the
coefficients or the sectoral splittings and how in both cases the use of
sectoral splittings may need some a-priori assumptions on the rotation.
Then, Section 3 presents the different
inverse methods used and, finally, we discuss the results obtained in Section
5