  Among magnetar models of Fast Radio Bursts (FRBs), there is ongoing debate
about whether the site of coherent radio emission lies within or beyond the
light cylinder. We propose a mechanism by which FRBs produced near the magnetar
surface are transported out of the magnetosphere by axions, which couple to
photons. If the emission site hosts strong accelerating electric fields, a
considerable fraction of the FRB energy budget is converted to an axion burst.
Once produced, the axion burst free-streams out of the magnetosphere due to the
rapidly-decreasing magnetic field. The burst may escape through either the open
or closed magnetosphere, while retaining the temporal signature of the original
FRB. In the wind region, axions resonantly excite ordinary (O) modes that
escape as the plasma density decreases. The radio efficiency of this mechanism
satisfies energetics constraints from FRB 121102 for axion-photon coupling
strengths that have not been excluded by other astrophysical probes.
