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Diagnostics of the Interaction between Seismic Waves and Photospheric Magnetic Fields

Diagnostics of the Interaction between Seismic Waves and Photospheric Magnetic Fields. Charles Lindsey Doug Braun Aaron Birch Paul Cally Alina Donea Hannah Schunker Ashley Crouch. Travel Time Signatures into Surface Magnetic Regions. Ingression control correlation phase shift

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Diagnostics of the Interaction between Seismic Waves and Photospheric Magnetic Fields

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  1. Diagnostics of the Interaction between Seismic Waves and Photospheric Magnetic Fields Charles Lindsey Doug Braun Aaron Birch Paul Cally Alina Donea Hannah Schunker Ashley Crouch

  2. Travel Time Signatures into Surface Magnetic Regions • Ingression control correlation phase shift • Discovered by Duvall et al. • Travel time reduction • Penumbral phase anomaly

  3. The Phase Inequality • Travel times into active regions are up to 30 sec greater than for outgoing waves (Duvall et al. 1996). • Possible contributorss: • downflows • damping (magnetic?)

  4. Penumbral Phase Anomaly • A) Continuum Intensity • B) Line-of-sight magnetic field • C) Square horizontal magnetic field • Ingression control correlation

  5. Penumbral Phase Anomaly in a Small Isolated Sunspot • A) Continuum intensity • B) Line-of-sight magnetic field • C) Square horizontal magnetic field • D) Ingression control correlation

  6. Downflows • Considerations of mass conservation (Lindsey and Braun 1996): Downflows appear to conflict with other signatures suggesting horizontal outflows. 2 pi r Vr H = p r^2 Vz Vr = (r/2H) vz

  7. Downflows • Zhao and Kosovichev (2003) • Downflows of order 0.5 km/sec • Comparable horizontal inflows • Fractional rate of change of density up to 0.0001/sec

  8. Magnet Damping • Inclined penumbral magnetic fields suggest control experiments to discriminate magnetic effects from those of flows.

  9. The “Schunker et al. Effect” • Dependence of the ingression control correlation on vantage with respect to an inclined magnetic field.

  10. The Schunker Effect and Travel Times • As we presently understand it, the Schunker et al. effect introduces a vantage-dependence to the phase inequality.

  11. Control Computations for the Schunker et al. Effect • 1-dimensional numerical modeling to determine holographic signatures of waves impinging into uniform photospheric magnetic regions (Crouch et al.)

  12. Control Consideratiosn Respecting Locality • The thinness of the region of effective mode conversion suggests that magnetic effects can be confined to the local magnetic field. • Numerical tests of locality • Locality would make corrections to the showerglass far more practical.

  13. Conclusions • Helioseismic signatures show strong evidence for large phase shifts introduced photospheric magnetic fields into helioseismic signatures. • Magnetically induced phase shifts may well predominate certain helioseismic signatures, the travel time inequality in particular. • Helioseismic signatures show strong evidence of mode coupling between p-modes and Alfven waves suggested by Cally and Bogdan. • A careful account for magnetically induced phase shifts is essential for subphotospheric flow diagnostics.

  14. Questions(?) Photo from home page of Natalia Dziourkevitch: http://www.aip.de/~nsd

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