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Title: Comparison of GONG and MDI sound-speed anomalies beneath two active regions
Authors: Hughes, S. J
Rajaguru, S. P
Thompson, M. J
Keywords: Sun: Activity;Sun: Oscillations;Sunspots
Issue Date: Oct-2004
Publisher: European Space Agency
Citation: D. Danesy., ed., Proceedings of the SOHO 14 / GONG 2004 Workshop (ESA SP-559). "Helio- and Asteroseismology: Towards a Golden Future". 12 - 16 July, 2004. pp. 493 - 496
Series/Report no.: ESA SP; No. 559
Abstract: Travel times of acoustic waves are calculated from Dopplergrams of solar oscillations obtained using the Global Oscillation Network Group (GONG) ground-based network and the Michelson Doppler Imager (MDI) instrument on board the SOHO satellite. These travel times are invested using a standard ray approximation to ascertain the sound-speed anomalies below two active regions. Some simple methods for ignoring the possibly corrupted measurements from within a sunspot are considered, as are diagnostics fro optimizing the inversion. Results are then presented for two different spot regions and the results of the instruments are compared: both regions behave in similar ways and the agreements between the two instruments is good. First-skip and second-skip data are found to produce similar results for deeper layers of the model, but the significance of the shallower results from second-skip data is questionable. We conclude that the use of GONG data fro time-distance analysis is appropriate.
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Appears in Collections:IIAP Publications

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