  We calculate the self force acting on a scalar particle which is falling
radially into a Schwarzschild black hole. We treat the particle's self-field as
a linear perturbation over the fixed Schwarzschild background. The force is
calculated by numerically solving the appropriate wave equation for each mode
of the field in the time domain, calculating its contribution to the self
force, and summing over all modes using Ori's mode-sum regularization
prescription. The radial component of the force is attractive at large
distances, and becomes repulsive as the particle approaches the event horizon.
