Title: 
==============
Spatial and temporal mapping of horizontal velocity flows.

Lead Investigator:
=======
Jesu's Patro'n Recio, Instituto de Astrofi'sica de Canarias. jpr@iac.es

Team Members:
==================
Irene Gonza'lez Herna'ndez, Instituto de Astrofi'sica de Canarias. iglez@iac.es
Frank Hill
Deborah Haber
(Open to collaborate with interested people)     

Local Coordinator:
==================
Rick Bogart (or anybody you think is suitable)

Lead Programmer:
=====
Luiz Sa' (or anybody you think is suitable)

Technical Summary:
==================
   Ring diagrams analysis techniques will be applied to MDI-SOI
images in order to obtain a whole map of horizontal velocity
flows at 360 degrees of longitude and up to +/-50 or +/-70 degrees
in latitude. At the same time a single or several subraster of the
solar surface will be tracked over several solar rotations to 
study the temporal evolution of the velocity flows.     

Proposal Text:
=======================
	The analysis of tridimensional power spectra of solar
oscillations has proven to be a powerfull tool to understand and
measure horizontal velocity flows under the solar surface (1). This
technique, know as the 'ring diagram' analysis, provides us with
local information rather than global, so that a tridimensional map 
of horizontal velocity flows can be constructed in latitude, 
longitude and depth in the solar globe (2).

The knowledge of the dynamic state of the solar interior is a big step
towards understanding the mechanisms of the convection fenomena and,
even more, the conection between magnetic and dynamic effects.

Ring diagram techniques are relatively young, and several solar
phisicists are working to test and improve the analysis procedure (3).
The solar oscillation group at the IAC in Canary Islands is participating
in this improvement by the analysis of Mt. Wilson data (4) and, since
last summer (1994), TON (Taiwan Oscillation Network) data (5). Several
test have also been performed lately with GONG data.

MDI(SOI) gives us a great oportunity to continue and improve the
development of the ring diagram analysis technique. The quality of
non-terrestrial atmospheric-affected images, together with a 
continuous set of data with no night-time gaps will provide us
with probably the best high resolution set of data available today.
Eventually, this will make easier the task of the detection of
systematic errors in the ring diagram procedures, and also the
fitting of the rings, a very hard task right now.

The working program we try to develop by using MDI-SOI products
is intended to provide a more continuous map of the horizontal
velocity flows in a wide region around solar equator up to +/-50
or +/-70 degrees of latitude and 360 degrees of longitude.
The smallest amount of data required for this purpose will correspond
to the time span of a solar rotation (about 30 days).

Another aspect we want to study is the temporal evolution of the
velocity flows. In order to perform these studies we need to track
a single or several subrasters of the solar disk as longer as we
can. Probably sets of about 3 or 4 days of data in every solar
rotation will be enought for our purposes. The temporal evolution
of the velocity flows can give us some answers about the evolution
of the magnetic activity of the solar surface and the solar cycle
and dynamo effects.

See Also:
=========
1.-Hill,F.,1988,Ap.J.,333,p:996
2.-Patro'n,J.,1994,PhD Thesis.
3.-Haber,D.,et al,1995, in ASP Conferences Series, Vol.76,GONG 1994: Helio
and asteroseismology from the earth and space,ed R.K. Ulrich,E.J.Rhodes,
Jr.,and W. Dappen.
4.-Patro'n,J.,et al,1995,Ap.J.,in press.
5.-Gonza'lez,I.,et al,1995,Proceedings of the V SOHO Workshop, in press.