A Critical Evaluation of Recent Claims Concerning Solar Rotation

Fossat et al. recently reported detecting rotational splitting of g-modes indirectly via the interaction with p-modes observed directly by the Global Oscillations at Low Frequency (GOLF) instrument on the Solar and Heliospheric Observatory (SOHO). They concluded that the core of the Sun is rotating 3.8 +/- 0.1 times faster than the surrounding radiative envelope. This is startling, partly because such rapid rotation almost contradicts direct inferences from the p-mode rotational splitting inferred from the same data. Moreover, the inferred amplitudes of the g-modes appear to exceed the upper bound reported by Appourchaux et al. It is also suspect because the theory of the procedure implies that the principal modes claimed to have been measured should be undetectable. We point out that there are other interpretations: one leads to a core rotation about twice as fast as the surrounding envelope; another, to a core rotating more slowly than the envelope. Here we also report on an independent assessment of the Fossat et al. analysis by applying their procedure to different representations of the GOLF data, expanding on Schunker et al. We also analyze seismic data obtained from LOI and MDI (both also on SOHO), from HMI (on SDO), and from the ground-based BISON and GONG, and we find the evidence reported by Fossat et al. not to be robust. We also illustrate that merely fitting model spectra to observations, which Fossat et al. do to support their g-mode detections, and as Fossat & Schmider do for extracting additional g-mode splittings, is not necessarily reliable. We are therefore led to doubt the claim.