This thesis describes a helioseismic quest to determine the angular velocity inside the Sun as a function of depth and latitude. I analyze rotational frequency splittings extracted from 15 days of full-disk observations of the solar acoustic oscillations (1 = 15-99) obtained with the Fourier Tachometer (a Doppler analyzing instrument design by Tim Brown). I have compared the observed frequency splittings to those generated by several different physically -motivated models for the solar internal angular velocity. I also introduce convenient preliminary analysis techniques, which require no formal computations and which guide the choices of rotation models. My analysis suggests that the differential rotation in latitude observed at the solar surface pervades the convection zone and perhaps even deeper layers. Thus, the convection zone appears to contain little or no radial gradient of angular velocity. The analysis further indicates that the angular velocity of the outer portion of the radiative interior is constant, or nearly so, at a value that is intermediate between the relatively fast equatorial rate and the slower polar rate of the surface profile. This new picture of the Sun's internal rotation implies that a significant radial gradient exists only in a transitional layer between the convection zone and the radiative interior. The sign of the gradient in this layer reverses at a latitude of about 30 degrees, where the angular velocity of the "surface" profile at the base of the convection zone matches that of the interior: angular velocity decreases inward at latitudes below 30 degrees and increases inward at higher latitudes. This model has intriguing implications for the solar dynamo, for the current distribution and transport of angular momentum, and for the rotational and evolutionary history of the Sun. Frequency splittings from a novel reduction of higher degree oscillations (1 ~ 140-400), which potentially contain more detailed information on the rotation in the outer portions of the solar convection zone, provide limited corroboration of the lack of a radial gradient in the convection zone. However, the scatter in the extracted splittings makes this an uncertain conclusion. Corroboration of the new picture of solar internal rotation must await further observation. (Abstract shortened with permission of author.).
- Pub Date:
- Physics: Astronomy and Astrophysics