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

Helioseismic inferences (internal structure, plasma flows, etc) are often derived from the Doppler shifts of the spectral lines observed in the solar atmosphere. We investigate the impact on the power spectral density of oscillations obtained from Dopplergrams by 3 different methods: SDO/HMI line-of-sight pipeline, bisector method and center of gravity. The Doppler shifts were calculated using the synthetic Fe I 6173Å spectral lines generated for a 3D radiative hydrodynamic simulation StellarBox of the quiet Sun atmosphere and convection zone. Power spectra from the three Dopplergrams were compared with the power spectra from the simulated atmospheric velocities at the typical solar oscillation frequencies of 2.5 mHz – 4.5 mHz. The results indicate that near the disk center, the power spectra densities have the same behavior, but increasing differences emerge with large heliocentric angles. Of the three methods, it is observed that the center of gravity consistently gives the least contrast in power spectrum densitystructures. In addition, Pearson correlation analysis of the atmospheric velocities at different heights with Doppler shifts confirms that all three methods probe the similar atmospheric formation height of roughly 200km above the solar photosphere at disk center and at higher heights closer to the limb.