Localized averaging kernels for probing the deep meridional flow with data from GONG, MDI and HMI

Abstract

The Fourier-Legendre decomposition (FLD) method to study wave absorption in sunspots is a helioseismic technique which is also suited for the measurement of the meridional flow. Because the FLD method is sensible to low-degree oscillation modes, it bears the potential to be used to probe the average meridional flow in much deeper layers as it is currently possible with other methods. In order to rate the suitability of the available data for inversions of the deep flow, we compare localized averaging kernels as computed with data from the Global Oscillation Network Group (GONG), the Michelson Doppler Imager (MDI) aboard the SOHO spacecraft and also with preliminary data from the Helioseismic and Magnetic Imager (HMI) aboard the SDO spacecraft.