Authors: Isaac Asante (Georgia State University), Viacheslav Sadykov (Georgia State University), Irina Kitiashvili (NASA Ames Research Center)

Solar oscillations are reliable diagnostic tools for understanding the interior dynamics of the Sun. The observed frequencies of the oscillations allow us to probe varying depths beneath the solar photosphere. Doppler velocity is one of the common observables from which the solar oscillation frequencies are derived. Therefore, observable processing pipelines from which Doppler velocities are derived are crucial in obtaining an accurate understanding of the solar sub-surface flows and structures. Using 3D radiative hydrodynamic StellarBox simulations of the quiet Sun, we analyze the effects of three Doppler velocity methods on the observed frequencies of solar oscillations: SDO/HMI line-of-sight pipeline, the bisector method, and center of gravity. The Doppler velocities derived from these methods are compared with actual plasma velocities in the simulations, specifically, in the context of the local helioseismology methods (ring diagram analysis). The power spectra of solar oscillations are obtained from ring diagrams and analyzed at three frequencies: 2.5mHz, 3.5mHz and 4.5mHz. Our results show that (1) deviations in oscillation power spectra rise with the oscillation frequency, (2) the deviations increase with heliocentric angle away from the solar disk center, (3) the bisector method yields lower deviations in the power spectra compared to the other two pipelines at all frequencies and disk locations.  The deviations recorded have no notable dependence of the oscillation mode analyzed (f, p1 or p2 modes). Our analysis helps quantify the uncertainties in the ring diagram power spectrum and related helioseismic inferences arising from the choice of the particular Doppler velocity assessment technique.