VARIABILITY OF SURFACE FLOWS ON THE SUN AND THE IMPLICATIONS FOR EXOPLANET DETECTION

The published Mount Wilson Doppler-shift measurements of the solar velocity field taken in 1967-1982 are revisited with a more accurate model, which includes two terms representing the meridional flow and three terms corresponding to the convective limb shift. Integration of the recomputed data over the visible hemisphere reveals significant variability of the net radial velocity at characteristic time scales of 0.1-10 years, with a standard deviation of 1.4 m s(-1). This result is supported by independent published observations. The implications for exoplanet detection include reduced sensitivity of the Doppler method to Earth-like planets in the habitable zone, and an elevated probability of false detections at periods of a few to several years.