Solar Rotation and Large-Scale Flows Determined by Time-Distance Helioseismology from SOHO/MDI

P.M. Giles, Stanford University, U.S.A.; T.L. Duvall, Jr., NASA Goddard Space Flight Center, U.S.A.; and A.G. Kosovichev Stanford University, U.S.A.

Abstract

We use differences of reciprocal travel time of acoustic waves propagating along parallels and meridians to determine variations of solar rotation and large-scale flows beneath the Sun's surface. This new technique can provide an effective measure of the antisymmetric component of the differential rotation and meridional flows that are not determined by the traditional helioseismic techniques based on inversion of frequency splitting of normal modes. We investigate resolution and precision of the time-distance measurements using the Michelson Doppler Imager (MDI) Medium-l data. The first results show a clear picture of the latitudinal differential rotation and its variation with depth. We discuss preliminary results of the meridional flow measurements.