Ring-Diagram Analysis of Data From the Mt Wilson Magneto-Optic Filter

Maria Cristina Rabello-Soares, Richard S. Bogart
Stanford University, CSSA - HEPL A202
Stanford, Calif. 94305-4085, U.S.A.

Sarbani Basu
Astronomy Department, Yale University, P. O. Box 208101, 
New Haven Conn. 06520-8101, U. S. A.

Deborah A. Haber
JILA / University of Colorado, 440-UCB
Boulder, Colo. 80309-0440

Edward J. Rhodes, Perry Rose
Dept of Physics and Astronomy, University of Southern California, Mail Code 32
Los Angeles, Calif.  90089

Full-disc high-resolution (4") Doppler data are available at a one-minute
cadence on a near-daily basis from the Magneto-Optic Filter on the Mt Wilson
60-ft Tower Telescope from 1988 onwards.  Although coming from an instrument
that is less stable than the space-based MDI and has a lower duty cycle than
the 6-site GONG+ network, the Mt Wilson series is virtually the sole source
of data extending back before 1996 to which the techniques of local-area
heleioseismology might be usefully applied.  Ring-diagram analysis, which
in many respects is just an extension of the techniques of high-degree
global-mode helioseismology, is particularly promising for these data.
Here we report on initial analyses of selected time samples from the
Mt Wilson data series, comparing them where possible with results obtained
from other data sources during periods of overlap.