Helioseismic Holography

Principal Investigator /Institution:  Charles A. Lindsey/NOAO
Co-Investigator:  Douglas C. Braun/HAO

This proposal envisions a one-year program in helioseismic holography utilizing 
SOHO MDI observations to develop prospects for using p-modes in the 3-4 mHz 
range for diagnostics of surface and subsurface magnetic structure.

Local helioseismic diagnostics show clear signatures of the interaction of 
acoustic waves with magnetic regions.  Relatively little is understood 
of the physical dynamics of some of these effects, such as absorption
of waves by sunspots and other surface magnetic regions.  Recent 
developments in local helioseismology show evidence of 
flows associated with active regions and of large-scale convection in 
the quiet Sun. Time-distance analysis of horizontal motion in the  
first SOHO observations clearly show the flows comprising the quiet-Sun 
supergranulation.  The program described here proposes to explore
the possibility of subsurface diagnostics of magnetic structure 
and flows using techniques in computational holography.  The database 
provided by SOHO's MDI experiment is the ideal medium for the 
application of local helioseismic diagnostics.

The prospect of viewing local subsurface magnetic regions and flows 
opens an entirely new dimension to helioseismology,
as to solar and stellar physics in general.  Local acoustic
diagnostics could revolutionize our understanding of the solar dynamo and the 
22-year activity cycle.  It may make it possible to anticipate solar 
activity far in advance of its emergence to the surface.  Solar
activity is important to our solar-terrestrial perspective.  Its
effects on the terrestrial atmosphere and on communications have 
been established for decades.  Its effects on satellites are 
critical and sometimes disastrous.  If we are to continue 
space exploration into the coming millennium, particularly manned
exploration outside of the near-earth environment, it will be 
essential that we understand solar activity as extensively as 
possible.  We are convinced that helioseismic holography is
essential for definitive diagnostics of solar activity.