Local helioseismic and spectroscopic analyses of interactions between acoustic waves and a sunspot

Abstract

Using a high cadence imaging spectropolarimetric observation of a sunspot and its surroundings in magnetically sensitive (FeI 6173 A) and insensitive (FeI 7090 A) upper photospheric absorption lines, we map the instantaneous wave phases and helioseismic travel times as a function of observation height and inclination of magnetic field to the vertical. We confirm the magnetic inclination angle dependent transmission of incident acoustic waves into upward propagating waves, and derive (1) proof that helioseismic travel times receive direction dependent contributions from such waves and hence cause errors in conventional flow inferences, (2) evidences for acoustic wave sources beneath the umbral photosphere, and (3) significant differences in travel times measured from the chosen magnetically sensitive and insensitive spectral lines.

arXiv comment12 pages, 5 figures, To appear in the Astrophysical Journal Letters

References in corpus (7)

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Cited by in corpus (6)

• Observables Processing for the Helioseismic and Magnetic Imager Instrument on the Solar Dynamics Observatory
• An Inside Look at Sunspot Oscillations with Higher Azimuthal Wavenumbers
• Properties of high-frequency wave power halos around active regions: an analysis of multi-height data from HMI and AIA onboard SDO
• Non-zero phase-shifts of acoustic waves in the lower solar atmosphere measured from realistic simulations and their role in local helioseismology
• Statistical analysis of acoustic wave power and flows around solar active regions
• On the propagation of gravity waves in the lower solar atmosphere in different magnetic configurations