Separating Surface Magnetic Effects in Sunspot Seismology: New Time-distance Helioseismic Diagnostics
نویسنده
چکیده
Time-distance helioseismic measurements in surfaceand deep-focus geometries for wave-paths that distinguish surface magnetic contributions from those due to deeper perturbations beneath a large sunspot are presented and analysed. Travel times showing an increased wave speed region extending down to about 18 Mm beneath the spot are detected in deep-focus geometry that largely avoids use of wave field within the spot. Direction (inor out-going wave) and surface magnetic field (or focus depth) dependent changes in frequency dependence of travel times are shown and identified to be signatures of wave absorption and conversion in near surface layers rather than that of shallowness of sunspot induced perturbations. Subject headings: Sun: helioseismology — Sun: magnetic fields — Sun: oscillations — sunspots
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