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 descriptions.

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 fields.

Chromospheric Structure

Analyze magnetic and thermal structures within the chromospheric acoustic cavity.

Excitation and Damping

Explore the coupling of acoustic-gravity waves to turbulent convection. Determine mode lifetimes, and elucidate the driving mechanisms.

Active Region Seismology

Measure the scattering and absorption of waves by active regions; search for wakes behind sunspots; search for pre-eruptive magnetic fields.

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 turbulence.

Magneto-hydrodynamics

Study MHD processes by simultaneous sampling of velocities, temperatures, and magnetic fields.

Supergranulation

Study evolution of supergranule convection cells and magnetic network reorganization.

Figure of the Limb

Study long-term variations in the figure of the limb.

Flux Budget

Spot and plage contribution to radiant flux.