  We report the first experimental detection of a zero-frequency fluctuation
that is pumped by an Alfv\'en mode in a magnetically confined plasma.
Core-localized bidirectional Alfv\'en modes of frequency inside the
toroidicity-induced gap (and its harmonics) exhibit three-wave coupling
interactions with a zero-frequency fluctuation. The observation of the
zero-frequency fluctuation is consistent with theoretical and numerical
predictions of zonal modes pumped by Alfv\'en modes, and is correlated with an
increase in the deep core ion temperature, temperature gradient, and
confinement factor $H_{89,P}$. Despite the energetic particle transport induced
by the Alfv\'en eigenmodes, the generation of a zero-frequency fluctuation that
can suppress the turbulence leads to an overall improvement of confinement.
