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Session 2 - Everything Else.
Display session, Friday, June 27
Ballroom C, Chair: Richard Canfield

[2.08] The Forward Problem in Sunspot Seismology

C. S. Rosenthal (HAO/NCAR), K. A. Julien (Applied Math Dept., University of Colorado)

Observations of the interaction of p\/-modes with sunspots show strong absorption and scattering which each show a systematic pattern of variation as a function of frequency and wavenumber. Our goal of inferring the sub-surface structure of sunspots from such data has been difficult to achieve because of the many complexities involved in the wave/spot interaction.

However, the basic wave-transformation processes involved are now relatively well understood. We have therefore proceeded to the next step of constructing a fully two-dimensional numerical model of the interaction of solar oscillations with a sunspot. In a simple slab geometry, in which the field is everywhere vertical, we find that modes confined to the region close to the surface show absorption and scattering profiles comparable to those measured on the Sun. However, deeper modes pass through our model sunspot virtually unaffected.

We conclude that our basic mode-transformation mechanism can adequately explain the properties of real sunspots, but that the actual structure of a sunspot must involve a magnetic field which increases substantially with depth below the photosphere if it is to explain the strength of the observed interaction.

Program listing for Friday