Please use this identifier to cite or link to this item: http://hdl.handle.net/2248/4272
Title: Impact of locally suppressed wave sources on helioseismic traveltimes
Authors: Hanasoge, S. M
Couvidat, S
Rajaguru, S. P
Birch, A. C
Keywords: Sun: helioseismology;Sun: oscillations
Issue Date: Dec-2008
Publisher: Royal Astronomical Society
Citation: Monthly Notices of the Royal Astronomical Society, Vol. 391, No. 4, pp. 1931 - 1939
Abstract: Wave traveltime shifts in the vicinity of sunspots are typically interpreted as arising predominantly from magnetic fields, flows and local changes in sound speed. We show here that the suppression of granulation related wave sources in a sunspot can also contribute significantly to these shifts, and in some cases, an asymmetry between ingoing and outgoing wave traveltimes. The tight connection between the physical interpretation of traveltimes and source-distribution homogeneity is confirmed. Statistically significant traveltime shifts are recovered upon numerically simulating wave propagation in the presence of a localized decrease in source strength. We also demonstrate that these time shifts are relatively sensitive to the modal damping rates; thus we are only able to place bounds on the magnitude of the effect of suppressed sources. We see a systematic reduction of 10–15 s in p-mode mean traveltimes at short distances (∼6.2 Mm) that could be misinterpreted as arising from a shallow (thickness of 1.5 Mm) increase (∼4 per cent) in the sound speed. At larger travel distances (∼24 Mm), a 6–13 s difference between the ingoing and outgoing wave traveltimes is observed; this could mistakenly be inferred as being caused by flows.
URI: http://hdl.handle.net/2248/4272
ISSN: 0035-8711
???metadata.dc.rights???: © Royal Astronomical Society
???metadata.dc.relation.uri???: http://arxiv.org/abs/0707.1369
http://dx.doi.org/10.1111/j.1365-2966.2008.14013.x
Appears in Collections:IIAP Publications

Files in This Item:
File Description SizeFormat 
Impact of locally suppressed wave sources on helioseismic traveltimes757.93 kBAdobe PDFView/Open


Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.