Solar Physics Division Meeting 2000, June 19-22
Session 2. Corona, Solar Wind, Flares, CMEs, Solar-stellar, Instrumentation, Other
Display, Chair: J. Krall, Monday-Thursday, June 19, 2000, 8:00am-6:00pm, Forum Ballroom

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[2.112] Seismic Imaging of the Far Side and Interior of the Sun

D.C. Braun (NWRA-CoRA & SPRC), C. Lindsey (SPRC)

Images of active regions on the far side of the Sun were derived by applying seismic holography to observations from the SOI-MDI instrument on the {\em SOHO} spacecraft. Synoptic seismic imaging of far-side solar activity will allow anticipation of the appearance of large active regions more than a week ahead of their arrival on the east limb. The technical requirements for a synoptic monitor appear to be quite modest, given real time access to observations from the Global Oscillations Network Group, for example. Currently, seismic images of the solar far side are easily computed in less than a day using a single-processor Pentium-based PC running Linux.

In addition to providing new applications for space weather prediction, the development of solar acoustic holography is opening major new diagnostic avenues in the study of the solar interior. Phase-sensitive seismic holography is producing high-resolution maps of sound travel-time anomalies caused by magnetic forces in the immediate subphotosphere, apparent thermal enhancements in acoustic moats around sunspots, and Doppler signatures of subsurface flows. Seismic holography applied to global modes, such as those used to image the far side, has directly demonstrated the influence of active regions on these modes. This reinforces a growing consensus that reduced sound travel times in magnetic regions explain the entirety of the frequency shifts of global modes with the solar cycle. Phase-sensitive holography will also be used to probe thermal and Doppler perturbations deep in the solar convection zone and the tachocline.

This work is supported by grants NAG5-7236 from NASA and AST-9528249 from NSF, and by a contract, PY-0184, from Stanford University.

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