SOI Science Objectives
The following is the list of science objectives detailed at the beginning
of the SOI program in 1987. The implementation plans for the
accomplishment of these objectives are contained in the
Team Science Investigation
The primary objective of the SOI investigation is to investigate the solar
interior using the tools of helioseismology. To fulfill the potential of
helioseismology, observations free of the distortions from the Earth's
atmosphere and free of diurnal data gaps must be obtained. The primary data
set consists of precision measurements of the line-of-sight surface velocity
field from which the oscillation modes of the solar interior can be deduced.
In addition to the primary objectives, the SOI program includes investigation
of several associated science objectives. They are called associated objectives
because they involve the study of observable solar phenomena using traditional
techniques, though they share the same goal of understanding the structure and
variability of the Sun. These investigations are no less important to the
understanding of the solar structure and dynamics than the primary objectives.
Primary Science Objectives
- Radial Stratification
Determine the spherically symmetric components of the mean
radial structure of the Sun in and below the convective envelope
of pressure, density, composition, and sound speed.
- Internal Rotation
Determine the rotation rate as a function of radius and latitude.
- Large-Scale Convection
Large-scale convection cells and associated thermal structures
- Large-Scale Asphericity
Determine the non-spherically symmetric components of the mean
structure in the convective envelope of pressure, density,
composition, and sound speed.
- Upper Convective Boundary Layer
Make a detailed sampling of the sub-surface regions by determining
the upper reflection point for most p-modes. Explore this
region dominated by highly turbulent convection and fibril magnetic
- Chromospheric Structure
Analyze magnetic and thermal structures within the chromospheric
- Excitation and Damping
Explore the coupling of acoustic-gravity waves to turbulent
convection. Determine mode lifetimes, and elucidate the driving
- Active Region Seismology
Measure the scattering and absorption of waves by active regions;
search for wakes behind sunspots; search for pre-eruptive magnetic
- Internal Global Scale Magnetic Fields
Determine the strength of the toroidal magnetic fields at the base
of the convection zone, and of the core fields.
- Seismic Response to Flares
Search for and analyze wave excitation by major flares.
Associated Science Objectives
- Large-Scale Surface Flows
Global surface flows: meridional circulation and giant cells;
temperature field associated with flows.
- Magnetic Fields
Magnetograms, for validation of velocity data and support
of other SOHO experiments.
- Turbulent Convection
Study granulation and mesogranulation, evolution and advection
of smallest-scale intensity features; study physics of intense
Study MHD processes by simultaneous sampling of velocities,
temperatures, and magnetic fields.
Study evolution of supergranule convection cells and magnetic
- Figure of the Limb
Study long-term variations in the figure of the limb.
- Flux Budget
Spot and plage contribution to radiant flux.
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