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R.M. Larsen, A.G. Kosovichev, J. Schou (Stanford)
Inversions of rotational frequency splittings derived from helioseismic data obtained by the MDI instrument and the GONG network have given a detailed picture of the differential rotation in the convection zone (Schou et al. 1998). However, features associated with sharp gradients of the rotation rate such as jets, near surface shear layers (torsional oscillations) as well as the transition layer to the radiative interior (the "tachocline") are usually not well resolved. This is due to the smoothing applied by traditional inversion methods such as Regularized Least Squares (RLS) and Optimally Localized Averages (OLA). In this work we show how a generalized version of the method proposed by Thompson (1990) can used be to study these features by inverting directly for the radial or latitudinal derivative of the rotation rate.
This research is supported by the SOI-MDI NASA grant NAG5-3077 at Stanford University.
References: \\ G.I. Marchuk, Methods of Numerical Mathematics, New York, Springer-Verlag, 1975. \\ Schou, J. et al., 1998, Astrophys J., 505, 390. \\ Thompson, M. J., 1990, Sol. Phys., 125, 1.
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