Solar Rotation Inversions from Splittings and from A-Coefficients

Abstract

From helioseismic telescope networks such as the Global Oscillation Network Group (GONG) and also from the Solar Heliospheric Observatory satellite (SoHO), helioseismologists now have data on in excess of 20000 oscillation frequencies v of the modes known collectively as the 5 minute oscillations. Depending on the order and degree of the modes these data are available either as individual frequencies of modes with known radial order n, spherical harmonic degree l, and order m, or as so-called ‘a-coefficients’ which are obtained by fitting polynomials to ridges of power in the (l, v) diagram.