Astronomy and Astrophysics – Astronomy
Scientific paper
Jul 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005apj...627.1040h&link_type=abstract
The Astrophysical Journal, Volume 627, Issue 2, pp. 1040-1048.
Astronomy and Astrophysics
Astronomy
18
Sun: Activity, Sun: Helioseismology, Sun: Oscillations, Sun: Sunspots
Scientific paper
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 inverted 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 for 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 agreement 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 GONG data are appropriate for time-distance analysis.
Hughes Shane J.
Rajaguru S. P.
Thompson Michael J.
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