Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 435, Issue 3, Pages 2589-2597Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stt1473
Keywords
Sun: helioseismology; Sun: magnetic fields; Sun: oscillations
Categories
Funding
- Merit Allocation Scheme on the NCI National Facility at the ANU
- Multi-modal Australian ScienceS Imaging and Visualisation Environment (MASSIVE)
- Swinburne Government's Education Investment Fund
- Australian Government's Education Investment Fund
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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 Alfven waves. The reflected fast and downgoing Alfven 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 Alfvenic 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 s 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.
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