Investigation Title:
High Resolution FOV Time-Distance Helioseismology.

Lead Investigator:
Peter Milford (Parallel Rules Inc.)

Team Members:
Tom Duvall (Stanford University)
Sasha Kosovichev (Stanford University)

SOI Coordinator:
Tom Duvall

SSSC Programmer:
Katie? Luiz?

Abstract/Technical Summary:
The goal is measure local solar subsurface properties by inverting time-dis-
tance data measured from high resolution field-of-view data.

The techniques of Time-Distance helioseismology have been/are being
applied to `full disk' resolution data. This SOI proposal is to work in con-
junction with the Team science objective `Time-Distance helioseismology'
to develop high resolution time-distance helioseismology.

Investigation Plan:

Goals:
Measure local solar properties as a function of depth and position. Corre-
late with surface conditions. Initially determine sound speed only, develop-
ing to flows and other quantities. Study structure and dynamics of small-scale
active phenomena such as sunspots.

Techniques:
Apply time-distance analysis to high resolution field of view doppler data.
Invert the data using techniques suitable for large datasets, such as conju-
gate gradient methods.

Observations:
The observations consist of High resolution field of view dopplergrams,
probably a minimum of 8 hour periods, with a few interspersed magneto-
grams.

Associated Investigations:
This investigation uses different techniques but has similar goals to the
Rings analysis, which determines sub-surface flows using other methods. It
complements the global time-distance analysis and the surface correlation
tracking measuring surface flows.

Approximate initial task list:

1.	Adapt the existing Time-distance analysis techniques to the require-
ments of a smaller field-of-view.

2.	Depending on timeline, either use early 8 hour MDI HR observations
or import existing 10 hour LaPalma dataset as a test dataset. Consider
artificial datasets.

3.	Using test dataset tune the analysis for the smaller field-of-view.
Understand in detail issues such as noise, spatial and temporal trade-
offs etc.

4.	Further develop the inversions, initially for sound speed then flows.


References:
"Time-Distance Helioseismology",
T.L. Duvall Jr., S.M. Jefferies, J.W. Harvey, M.A. Pomerantz,
Nature 362, 430-432, 1993.

The Frequency Variation of Solar Acoustic Wave Travel Times",
T.L. Duvall Jr., S.M. Jefferies, J.W. Harvey, M.A. Pomerantz,
proceedings of Applications of Time Series in Astronomy
and Meteorology, a meeting held in Padova, Italy, Sept. 1993,
ed. O. Lessi, 179-182.

"Use of Acoustic Wave Travel Time Measurements to Probe the Near-Surface
Layers of the Sun", Jefferies, S.M., Osaki, Y., Shibahashi, H.,
Duvall, T.L. Jr., Harvey, J.W., and Pomerantz, M.A. 1994, Astrophys. J.434,
795-800.

"Time-Distance Helioseismology: An Update",
Duvall, T.L. Jr. 1994,
proceedings of the GONG '94 conference, 465-474.

"Time-Distance Helioseismology in the Vicinity of Sunspots",
D'Silva, S. and Duvall, T.L. Jr. 1994,
Astrophys. J. 438, 454-462.

"Mapping Wave Speed and Flows Below Solar Active Regions",
Duvall, T.L. Jr., D'Silva, S., Jefferies, S.M., Harvey, J.W., and
Schou, J., 1995, (in preparation).