2008/02/19 by D. C. Braun, A. C. Birch · 1 citation
Biochemistry, Genetics and Molecular Biology · Earth and Planetary Sciences · Physics and Astronomy · #Astrophysics #Computational physics #Filter (signal processing) #Geodesy #Geology #Geomagnetism and Paleomagnetism Studies #Geophysics and Gravity Measurements #Helioseismology #Holography #Magnetic field #Mode (computer interface) #Optics #Phase (matter) #Physics #Ridge #Solar and Space Plasma Dynamics #Sunspot #astro-ph
paper · pdf · doi:10.1007/s11207-008-9152-5
Solar Physics, accepted
arxiv created 2008/02/19 · openalex publication_date 2008/03/06 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present a comprehensive set of observations of the interaction of p-mode oscillations with sunspots using surface-focused seismic holography. Maps of travel-time shifts, relative to quiet-Sun travel times, are shown for incoming and outgoing p modes as well as their mean and difference. We compare results using phase-speed filters with results obtained with filters that isolate single p-mode ridges, and further divide the data into multiple temporal frequency bandpasses. The f mode is removed from the data. The variations of the resulting travel-time shifts with magnetic-field strength and with the filter parameters are explored. We find that spatial averages of these shifts within sunspot umbrae, penumbrae, and surrounding plage often show strong frequency variations at fixed phase speed. In addition, we find that positive values of the mean and difference travel-time shifts appear exclusively in waves observed with phase-speed filters that are dominated by power in the low-frequency wing of the p1 ridge. We assess the ratio of incoming to outgoing p-mode power using the ridge filters and compare surface-focused holography measurements with the results of earlier published p-mode scattering measurements using Fourier-Hankel decomposition.