Basic Principles of Seismic Holography
Abstract
Seismic imaging of the near solar interior using the basic principles of computational holography has given us a number of remarkable discoveries in the last two years. Seismic holography is accomplished by the phase-coherent wave-mechanical reconstruction of the p-mode acoustic field into the solar interior based on helioseismic observations at the solar surface. Seismic holography treats the acoustic field at the solar surface in a way broadly analogous to how the eye treats electromagnetic radiation at the surface of the cornea, wave-mechanically regressing radiation from distant sources to render stigmatic images that can sampled over any desired focal plane. Holographic diagnostics are designed to give us a straight-forward assessment of the information content of the observed p-mode spectrum independent of a physical model of the acoustic perturbations that give rise to the seismic signature observed at the solar surface. Computational holography was initially proposed as the optimum approach to the severe diffraction effects that confront standard tomography in the solar p-mode environment. The more general term "acoustic imaging" has recently been introduced to refer to this diagnostic concept. I will summarize the basic principles of the diagnostic in its broad generality as intuitively as possible, drawing on familiar principles in optics and the parallel with standard optical holography. I will discuss the diagnostic role of phase-sensitive holography and point out the parallels between this and time-distance- correlation measurements. Keeping in mind the critical distinction between holography and physical modeling, I will speculate into concepts that may offer us convenient avenues whereby to model solar interior acoustic perturbations based on a holographic presentation of solar interior acoustics.
- Publication:
-
SOHO-9 Workshop on Helioseismic Diagnostics of Solar Convection and Activity
- Pub Date:
- 1999
- Bibcode:
- 1999soho....9E..10L