A NEW INVERSION OF SOLAR ROTATIONAL SPLITTING DATA

The fine structure of the solar p-mode spectrum is used to obtain an estimate of the Sun's internal rotation rate, as a function of both latitude and depth, for fractional radii in the range 0.55 < r/R < 0.85. Because each piece of data is a weighted average of the rotation rate over an extended region of the solar interior and because the number of such measurements is finite, such an inversion unavoidably has limited resolution and suffers from other systematic errors. Accordingly, the results of the inversion presented here and other published inversions should be interpreted with this in mind. These problems are discussed in detail for the present inversion. Such systematic errors can be avoided by seeking not a functional form of the rotation rate but rather the values of suitably weighted averages of the rotation rate (or of functions derivable from it). Here it is shown that the value of a broad average over depth of the radial gradient of the solar rotation rate, concentrated in the convection zone, is consistent with the gradient being zero in this region but is apparently inconsistent with the picture of constant rotation on cylindrical surfaces aligned with the rotation axis. This result, which confirms the inference from the former type of inversion, is of importance for modelling the dynamics of the convection zone and also for dynamo models of the Sun's magnetic field. © 1990 Kluwer Academic Publishers.