"Global and Local Helioseismic Studies of Solar Convection Zone Dynamics Using SOI-MDI on SOHO." Dr. Juri Toomre, Principal Investigator JILA, University of Colorado, Boulder Dr. Joergen Christensen-Dalsgaard, Co-Investigator JILA, University of Colorado, Boulder & Theoretical Astrophysics Center, Aarhus University Dr. Douglas Gough, Co-Investigator JILA, University of Colorado, Boulder & Institute of Astronomy, University of Cambridge Dr. Deborah Haber, Co-Investigator JILA, University of Colorado, Boulder Dr. Bradley Hindman, Co-Investigator JILA, University of Colorado, Boulder Dr. Mike Thompson, Co-Investigator JILA, University of Colorado, Boulder & Queen Mary & Westfield College, University of London PROPOSAL SUMMARY The helioseismic observations by SOI-MDI on SOHO during the extended mission permit searches for changes in large-scale velocity fields and thermal structures within the highly turbulent convection zone as the sun proceeds into the magnetically active phase of its cycle. The inversions of global p-mode frequency splittings have provided estimates of the differential rotation profile established within that zone, revealing a tachocline of shear in the region of penetration at the base of the convection zone, and prominent shear layers close to the solar surface, which may include a submerged polar jet at high latitudes. There is expected to be a close linkage between such shearing flows and the solar dynamo, with the tachocline thought to be the site of organized magnetic dynamo action. Thus analysis of the helioseismic data to assess changes in the differential rotation profile and its shear zones as the magnetic cycle progresses may be very helpful in revealing aspects of the dynamo mechanism. We are here proposing to work on several major `key tasks' to help ensure that the vast high-resolution observational data sets from SOI-MDI will be analyzed in sufficient detail to be able to detect changes in the dynamics of the convection zone as the magnetic cycle advances, with our results to be correlated with TRACE observations on the emerging magnetic fields. We will use both global and local information deduced from the acoustic wave fields. As Task A we propose using global p-mode frequencies and their splittings through inversion to assess the variation with depth and latitude of sound speed and rotation rate within the solar envelope. High-degree oscillation mode data will be incorporated into the inversions to isolate effects of intense turbulence and rotational shear just below the solar surface that can otherwise lead to uncertainties in the inversions at greater depths. Two primary inversion procedures (2d-RLS and 2d-SOLA) will be employed for data sets that may sample as many as one million modes. Such major inversions require access to very substantial multi-processor computational facilities with large memories and disk systems, such as have been developed at the Helioseismic Analysis Facility (HAF) at JILA. In addition to using the global inversions to study temporal variations in the differential rotation profiles, including within the tachocline and in the near-surface shearing layer, efforts will be devoted to search for more intricate zonal jets and banded shearing flows. The use of high-resolution data from SOI-MDI also permits study of the acoustic wave fields in localized regions of the sun. The detailed shapes and displacements of the rings seen in 3-D power spectra can be used through inversion to study the variation with depth of horizontal flows and thermal and magnetic structures below those regions. We propose as Task B to apply ring-diagram analysis methods to arrays of localized regions that are tracked as the sun rotates, thus yielding mosaic mappings of the underlying flows and thermal fields. Such ring-diagram methods provide sensitive means for examining shearing flows and jets, large-scale coherent structures, and meridional circulations within the convection zone. Aspects of such flows are anticipated from recent developments in turbulence theory and are thought to have a crucial role in how angular momentum is redistributed by the convection to establish the differential rotation of the sun. New inversion procedures will be developed to combine information from many such samplings to yield broad 3-D spatial maps that evolve in time. Correlations will be sought between persistent flow patterns and active magnetic longitude sites, with intercomparison to be made with TRACE data that reveal the magnetic field eruption in detail. As Task C we propose to partially support the operation of HAF so that the computationally-intensive data analyses and inversions can carried out both by us and by other members of the dynamics and structure inversion teams associated with SOI-MDI. Our prior work as Co-I on SOI-MDI on the predecessor grant NAG 5-3077, `Solar Oscillations Investigation - M O & D A', has led to 14 publications which are referenced in the proposal.