Seismology of the Wounded Sun

Abstract

Active regions are open wounds in the Sun's surface. Seismic oscillations from the interior pass through them into the atmosphere, changing their nature in the process to fast and slow magneto-acoustic waves. The fast waves then partially reflect and partially mode convert to upgoing and downgoing Alfvén waves. The reflected fast and downgoing Alfvén waves then re-enter the interior through the active regions that spawned them, infecting the surface seismology with signatures of the atmosphere. Using numerical simulations of waves in uniform magnetic fields, we calculate the upward acoustic and Alfvénic losses in the atmosphere as functions of field inclination and wave orientation as well as the Time-Distance `travel time' perturbations, and show that they are related. Travel time perturbations relative to quiet Sun can exceed 40 seconds in 1 kG magnetic field. It is concluded that active region seismology is indeed significantly infected by waves leaving and re-entering the interior through magnetic wounds, with differing travel times depending on the orientation of the wave vector relative to the magnetic field. This presages a new directional-time-distance seismology.

10 pages, 8 figures, accepted for publication in MNRAS (Aug 5 2013)

References in corpus (3)

• Three Dimensional MHD Wave Propagation and Conversion to Alfven Waves near the Solar Surface. I. Direct Numerical Solution
• Seismic Halos Around Active Regions: An MHD Theory
• Magnetic and Thermal Phase Shifts in the Local Helioseismology of Sunspots

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• Chromospheric Heating by MHD Waves and Instabilities
• The Frequency-dependent Damping of Slow Magnetoacoustic Waves in a Sunspot Umbral Atmosphere
• 3D simulations of realistic power halos in magneto-hydrostatic sunspot atmospheres: linking theory and observation
• Detection of Fast-Moving Waves Propagating Outward along Sunspots' Radial Direction in the Photosphere
• Helioseismic Holography of Simulated Sunspots: dependence of the travel time on magnetic field strength and Wilson depression
• Helioseismic holography of simulated sunspots: magnetic and thermal contributions to travel times
• Directional Time-Distance Probing of Model Sunspot Atmospheres
• Sensitivity of helioseismic travel-times to the imposition of a Lorentz force limiter in computational helioseismology
• Statistical analysis of acoustic wave parameters near active regions
• Probing sunspots with two-skip time-distance helioseismology
• Conversion and Smoothing of MHD Shocks in Atmospheres with Open and Closed Magnetic Field and Neutral Points
• A Study of Acoustic Halos in Active Region NOAA 11330 using Multi-Height SDO Observations