Measurement of the Rotation Rate in the Deep Solar Interior

Abstract

We present a measurement of solar internal rotation based on observations obtained over 3 months in early 1994 with a new instrument called LOWL. This instrument allows for the simultaneous observation of low- and intermediate-degree solar oscillations with spatial resolution. We have measured the frequency splitting of 673 multiplets with degrees ranging from 1 to 80 and inverted these to derive an estimate of the solar internal rotation profile between 0.2 and 0.85 R☉. The accuracy of this measurement ranges from ~1% in the outer regions to ~5% at 0.2 R☉ and thus places better constraints than hitherto on the rotation in the deep solar interior. We confirm earlier findings that near the base of the convection zone the solar rotation profile undergoes a transition from surface-like differential rotation to a rotation rate that is independent of latitude. In addition, we find that from the base of the convection zone down to 0.2 R☉ our measurement is consistent with rigid body rotation at a rate somewhat lower than the surface equatorial rate. The accuracy of our measurement in the deep solar interior provides a strong constraint to theories of solar and stellar angular momentum transport.