  Stellar surface magnetoconvection (granulation) creates asymmetries in the
observed stellar absorption lines that can subsequently manifest themselves as
spurious radial velocities shifts. In turn, this can then mask the
Doppler-reflex motion induced by orbiting planets on their host stars, and
represents a particular challenge for determining the masses of low-mass,
long-period planets. Herein, we study this impact by creating Sun-as-a-star
observations that encapsulate the granulation variability expected from 3D
magnetohydrodynamic simulations. These Sun-as-a-star model observations are in
good agreement with empirical observations of the Sun, but may underestimate
the total variability relative to the quiet Sun due to the increased magnetic
field strength in our models. We find numerous line profile characteristics
linearly correlate with the disc-integrated convection-induced velocities.
Removing the various correlations with the line bisector, equivalent width, and
the V_asy indicator may reduce ~50-60% of the granulation noise in the measured
velocities. We also find that simultaneous photometry may be a key diagnostic,
as our proxy for photometric brightness also allowed us to remove ~50% of the
granulation-induced radial velocity noise. These correlations and
granulation-noise mitigations breakdown in the presence of low instrumental
resolution and/or increased stellar rotation, as both act to smooth the
observed line profile asymmetries.
