Observations are presented on the modulation by hydromagnetic waves (irregular periods ~30 s; Pi 2 classification) of particle (electron) precipitation during two small cosmic noise absorption events observed at geometric latitude ~60 ¿S (particle srift shell L>4). The particle precipitation and modulation occur in the region of a near linearly polarized hydromagnetic wave. The overall particle precipitation appears to be controlled by magnetospheric dynamics, while the modulation of the precipitation is controlled by the hydromagnetic waves.