Nearly Steady Photospheric Flows from SOHO/SOI D.H. Hathaway, Marshall Space Flight Center Data from the SOI/MDI instrument on SOHO will be analyzed to measure the various components of the Sun's photospheric flows. Techniques will be developed, tested, and refined to characterize the flow components and to look for solar cycle variotions in these characteristics. Numerical models of these flows will be used to provide a detailed comparison between theory and observations. Solar cycle variations in the Sun's rotation and differential rotation have been previously reported and are fairly well established. Variations in the meridional flow and the convective components are far less certain and require further study. A technique for extracting the axisymmetric meridional flow velocity has been developed by the investigator and will be used to monitor the Sun for variations during the rising phase of solar cycle 23. This same technique also measures the center-to-limb profile fo the convective blue shift produced by the unresolved granulation pattern. This profile will also be monitored for solar cycle variations. The larger convective flows (mesogranules, supergranules, and giant cells) are all resolved by the MDI instrument and can also be monitored for solar cycle variations. Although Doppler measurements only give the line-of-sight velocity, certain characteristics of this velocity signal do provide information on the nature of the vector velocity field. Techniques will be applied to determine how much of the flow is directed in the radial and horizontal directions as a function of the size of the convective element. Additional techniques should also allow for a determination of the relative strengths of the poloidal (curl free flow) and toroidal (divergence free flow) components. The effects of magnetic fields on the convective flows and on the Doppler velocity signal itself will be studied and characterized. This will allow for a better determination of the convection pattern, its association with magnetic elements, and its variation with the solar cycle. Analyses of GONG data and a preliminary analysis of SOI/MDI data indicate a giant cell component to the convection spectrum. A new technique will be tested and applied to MDI data to cleanly extract any velocity signal due to giant cell convection. The characteristics of this signal and its association with the Sun's global magnetic field pattern will be investigated. This investigation will increase our knowledge of those photospheric flows that are key components involved in shaping the Sun's magnetic field and driving solar variability. It will monitor the variations in those flows during the rise of the current sunspot cycle.