Abstract
We study the sensitivity of wave travel times to steady and spatially homogeneous horizontal flows added to a realistic simulation of the solar convection performed by Robert F. Stein, Ake Nordlund, Dali Georgobiani, and David Benson. Three commonly used definitions of travel times are compared. We show that the relationship between travel-time difference and flow amplitude exhibits a non-linearity depending on the travel distance, the travel-time definition considered, and the details of the time – distance analysis (in particular, the impact of the phase-speed filter width). For times measured using a Gabor wavelet fit, the travel-time differences become nonlinear in the flow strength for flows of about 300 m s−1, and this non-linearity reaches almost 60% at 1200 m s−1 (relative difference between actual travel time and expected time for a linear behavior). We show that for travel distances greater than about 17 Mm, the ray approximation predicts the sensitivity of travel-time shifts to uniform flows. For smaller distances, the ray approximation can be inaccurate by more than a factor of three.
Similar content being viewed by others
References
Benson, D., Stein, R., Nordlund, A.: 2006, In: Uitenbroek, H., Leibacher, J., Stein, R.F. (eds.) Solar MHD Theory and Observations: A High Spatial Resolution Perspective CS-354, Astron. Soc. Pac., San Francisco, 92.
Birch, A.C., Gizon, L.: 2007, Astron. Nachr. 328, 228.
Birch, A.C., Kosovichev, A.G., Price, G.H., Schlottmann, R.B.: 2001, Astrophys. J. 561, L229.
Braun, D.C., Birch, A.C.: 2006, Astrophys. J. 647, 187.
Braun, D.C., Birch, A.C., Benson, D., Stein, R.F., Nordlund, A.: 2007, Astrophys. J. 669, 1395.
Christensen-Dalsgaard, J., Däppen, W., Ajukov, S., Anderson, E.R., Antia, H.M., Basu, S., et al.: 1996, Science 272, 1286.
Couvidat, S., Rajaguru, S.P.: 2007, Astrophys. J. 661, 558.
Couvidat, S., Birch, A.C., Kosovichev, A.G.: 2006, Astrophys. J. 640, 516.
Couvidat, S., Gizon, L., Birch, A.C., Larsen, R.M., Kosovichev, A.G.: 2005, Astrophys. J. Suppl. 158, 217.
D’Silva, S.: 2001, Astrophys. J. 549, L135.
Duvall, T.L., Gizon, L.: 2000, Solar Phys. 192, 177.
Duvall, T.L., Jefferies, S.M., Harvey, J.W., Pomerantz, M.A.: 1993, Nature 362, 430.
Duvall, T.L., Kosovichev, A.G., Scherrer, P.H., Bogart, R.S., Bush, R.I., de Forest, C., Hoeksema, J.T., Schou, J., Saba, J.L.R., Tarbell, T.D., Title, A.M., Wolfson, C.J., Milford, P.N.: 1997, Solar Phys. 170, 63.
Georgobiani, D., Zhao, J., Kosovichev, A.G., Benson, D., Stein, R.F., Nordlund, A.: 2007, Astrophys. J. 657, 1157.
Gizon, L., Birch, A.C.: 2002, Astrophys. J. 571, 966 [GB02].
Gizon, L., Birch, A.C.: 2004, Astrophys. J. 614, 472 [GB04].
Hirzberger, J., Gizon, L., Solanki, S.K., Duvall, T.L.: 2007, Solar Phys. 251, 417.
Jackiewicz, J., Gizon, L., Birch, A.C., Duvall, T.L.: 2007, Astrophys. J. 671, 1051.
Kosovichev, A.G., Duvall, T.L.: 1997, In: Pijpers, F.P., Christensen-Dalsgaard, J., Rosenthal, C.S. (eds.) Proceedings of SCORe’96: Solar Convection and Oscillations and Their Relationship, Astrophysics and Space Science Library 225, Kluwer, Dordrecht, 241.
Kosovichev, A.G., Duvall, T.L., Scherrer, P.H.: 2000, Solar Phys. 192, 159.
Scherrer, P.H., Bogart, R.S., Bush, R.I., Hoeksema, J.T., Kosovichev, A.G., Schou, J., et al.: 1995, Solar Phys. 162, 129.
Stein, R.F., Nordlund, A.: 2000, Solar Phys. 192, 91.
Zhao, J., Kosovichev, A.G.: 2003, In: Sawaya-Lacoste, H. (ed.) Proceedings of SOHO 12 / GONG+ 2002. Local and Global Helioseismology: The Present and Future SP-517, ESA, Noordwijk, 417.
Zhao, J., Kosovichev, A.G., Duvall, T.L.: 2001, Astrophys. J. 557, 384.
Zhao, J., Georgobiani, D., Kosovichev, A.G., Benson, D., Stein, R.F., Nordlund, A.: 2007, Astrophys. J. 659, 848.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Couvidat, S., Birch, A.C. Helioseismic Travel-Time Definitions and Sensitivity to Horizontal Flows Obtained from Simulations of Solar Convection. Sol Phys 257, 217–235 (2009). https://doi.org/10.1007/s11207-009-9371-4
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s11207-009-9371-4