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Session 10 - SOHO Helioseismology II, Interior.
Oral session, Saturday, June 28
Ballroom A, Chair: Thomas Bogdan

[10.02] Solar Meridional Circulation and Rotation Determined by Time-Distance Helioseismology using MDI Data From SOHO

P. M. Giles (CSSA, Stanford), T. L. Duvall Jr. (NASA/GSFC), A. G. Kosovichev (HEPL, Stanford), P. H. Scherrer (CSSA, Stanford)

Using the technique of time-distance helioseismology, acoustic wave travel times can be measured between pairs of points on the solar surface. The travel time of the waves depends primarily on the wave group velocity and on the component of flow velocity which is parallel to the direction of wave propagation. By choosing pairs of points which share a common longitude, it is possible to use these waves to probe the meridional flow beneath the surface. Any flows present will cause a difference between the northward and southward travel times along the meridian. Varying the distance between points allows isolation of waves which propagate to different depths beneath the surface, and thus the flow velocity can be measured as a function of latitude and depth.

Similarly, by choosing pairs of points which share a common latitude it is possible to measure the effects of solar rotation using an analogous procedure. This technique could provide high resolution in latitude and allows study of the northern and southern hemispheres independently.

Using velocity images taken by the Michelson Doppler Imager during June 1996, we have detected meridional flows in the uppermost layers of the sun. Measurements of this flow velocity and of the rotation rate as functions of latitude and depth will be presented. This research is supported by NASA contract NAG5-3077 at Stanford University.


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