Measurements of helioseismic travel times
Max-Planck-Institut für Sonnensystemforschung
Main category
Natural Sciences (Astrophysics and Astrononmy)
In time-distance helioseismology wave travel times are measured from the cross-correlation between Doppler velocities recorded at any two locations on the solar surface. All local helioseismology inferences rely critically on the definition of travel time and its accuracy. We compare two different methods to extract the travel times from the noisy cross-correlation functions. The first method consists of fitting a 5-parameter analytic function to the cross-correlation to obtain the phase travel time. The second method consists of linearizing the distance between the observed cross-correlation and a sliding reference cross-correlation (the only parameter is the travel time). We find that the one-parameter fits are more robust with respect to noise. Using SOHO data from the MDI Structure Program for the years 1996–2003, we study in detail the statistical properties of the noise associated with the travel-time measurements for the two different fitting methods.
Further information
Further reading
Roth, M., Gizon, L., Beck, J.G., 2007, Measuring helioseismic travel times, Astronomical Notes 328, 215
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