Estimated values of the weighted sum , using the observed B-coefficients obtained after considering the coupling between acoustic modes with Δℓ = 1 (left panel) and 3 (right) is plotted here. Upper and lower panels: results from analyses of 4 and 8 years of SDO/HMI data, respectively. The power for each azimuthal order, t, has been normalized. The black-dashed line is the theoretical dispersion relation for a uniformly rotating fluid with rotation frequency Ω/2π = 453 nHz. Modes with even azimuthal orders ranging from t = 2 to 16 are shown here.