Solar Physics Division Meeting 2000, June 19-22
Session 1. Helioseismology, Magnetic Fields, Chromosphere and Transition Region
Display, Chair: C. U. Keller, Monday-Thursday, June 19, 2000, 8:00am-6:00pm, Forum Ballroom

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[1.20] Diagnostics of Solar Magnetic Fields by Time-Distance Helioseismology

J. Zhao (Stanford University), T.L. Duvall, Jr (Laboratory for Astronomy and Solar Physics, NASA GSFC), A.G. Kosovichev (Stanford University)

Sunspot seismology has been developed in recent years, and the time-distance analysis plays an important role in it. Most of the current inferences for interior structures were made by measuring perturbations of the acoustic wave speed which is due to both temperature and magnetic field variations. An important problem of the time-distance seismology is to disentangle the effects of temperature and magnetic field. The standard technique for the travel time measurements is to divide annuli for given wave travel distances into four sectors to get both the wave speed and flow velocity under the surface. Here, we consider the inhomogeneity caused by the magnetic field of sunspots. By dividing the annuli into eight sectors and analyzing the travel time of each octants, we can obtain the direction and the magnitude of the magnetic field in sunspot regions. Scattering and absorption of incoming waves in each different direction may also play an important role in these measurements.


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