  Pulsar magnetospheres admit non-stationary vacuum gaps that are characterized
by non-vanishing ${\bf{E}} \cdot {\bf{B}}$. The vacuum gaps play an important
role in plasma production and electromagnetic wave emission. We show that these
gaps generate axions whose energy is set by the gap oscillation frequency. The
density of axions produced in a gap can be several orders of magnitude greater
than the ambient dark matter density. In the strong pulsar magnetic field, a
fraction of these axions may convert to photons, giving rise to broadband radio
signals. We show that dedicated observations of nearby pulsars with radio
telescopes (FAST) and interferometers (SKA) can probe axion-photon couplings
that are a few orders of magnitude lower than current astrophysical bounds.
