Calibration & Intercomparison of Data from MDI, GOLF, & Mt. Wilson R.K. Ulrich, UCLA The research by the group supported by this proposal has as a long-term goal the study of energy generation, transfer and transformation in the solar interior and through the solar atmosphere. The processes involved are fundamental to our understanding of the solar cycle of activity. In this proposal we emphasize three particular components of solar energetics: a) the structure and rotation of the energy generating solar core; b) large-scale convective patterns in the surface regions; c) mhd oscillations in the solar atmosphere. Our primary data will come from two helioseismology instruments on SOHO: MDI and GOLF with supporting data coming from the ground-based system of the 150-foot solar tower on Mt. Wilson. This part of the program is an extension of studies carried out as a Co-Investigator on MDI and GOLF. Task a), the study of the solar core, is based on the identification and measurement of low degree coherent solar oscillations having the lowest accessible frequencies. Such oscillation modes may include those whose primary restoring force is the gravitational force perturbation (g-modes) rather than the pressure force perturbation (p-modes). Such coherent g-mode oscillations would have great diagnostic power if convincingly identified but there is no assurance that they will have amplitudes large enough to stand out above the solar incoherent signals. Fortunately, even the long period p-modes have great diagnostic capability and the extension of the identifications to the lowest possible frequency is the assuredly realizable part of our project. This task has the highest priority during at least the first year of the project and perhaps for the full three year duration. Our approach to the identification of the low frequency/low amplitude oscillations is to carefully calibrate both MDI and GOLF so their data sequences are on a comparable basis. We will then: 1) carry out a crossed-amplitude study of the power spectra; 2) combine the two calibrated time series in order to put MDI on an atomic standard; 3) utilize the fact that GOLF integrates over the solar image unevenly to extract a new data sequence from MDI which is in some sense orthogonal to the GOLF data; 4) examine disk center sequences from the atomic calibrated MDI sequence to utilize the horizontal nature of the solar supergranulation velocities. The Mt. Wilson system provides simultaneous line profile maps of the solar surface using both the radiation of the line 676.8 nm utilized by MDI and of the Na D1 line utilized by GOLF. These maps will provide information concerning the height dependence of the various solar velocity signals and allow us to correct for these effects in comparing MDI and GOLF. Task b), the study of large-scale convective elements goes directly to the heart of the dynamo process. Material motions dominate the evolution of magnetic fields over most of the sun's convective envelope and these largest scale velocity fields provide the most direct linkage between observation and theory. The only well observed large scale velocity field having more structure than the differential rotation is the pattern known as the torsional oscillations. Recent analysis of data from Mt. Wilson shows that there is persistent longitudinal structure in this velocity field. We will use long-term flow maps derived from MDI data to compare to the Mt. Wilson data to more completely determine the spatial and temporal structure of these features. Task c) seeks to improve our understanding of the role of magnetic fields in transporting energy through the sun's atmosphere. In particular we will study the oscillatory behavior of the magnetic, velocity and intensity fields in an effort to determine the nature and strength of any magnetohydrodynamic waves which might be present in the sun's atmosphere. We have obtained a number of MDI campaign sequences which provide high time cadence magnetic measurements. We have explored the role of possible misregistration of the images in differing polarization and determined that this potential problem does not prevent the study from going forward. We will make collaborative observations between MDI campaigns and the Mt. Wilson new 24-channel spectrograph system in order to explore vertical phase relations for altitudes between the low photosphere and the low chromosphere. We will also propose to the TRACE team to include observations of the Transition Region in this collaborative observational effort.