  Prominences and cavities are ubiquitously observed together, but the physical
link between these disparate structures has not been established. We address
this issue by using dynamic emission in the extreme ultraviolet (EUV) to probe
the connections of these structures. The SDO/AIA observations show that the
cavity exhibits excessive emission variability compared to the surrounding
quiet-sun streamer, particularly in the 171\AA bandpass. We find that this
dynamic emission takes the form of coherent loop-like brightening structures
which emanate from the prominence into the central cavity. The geometry of
these structures, dubbed prominence horns, generally mimics the curvature of
the cavity boundary. We use a space-time statistical analysis of two cavities
in multiple AIA bandpasses to constrain the energetic properties of 45 horns.
In general, we find there is a positive correlation between the light curves of
the horns in the 171\AA and 193\AA bandpasses, however the 193\AA emission is a
factor of 5 weaker. There is also a strong correlation between structural
changes to the prominence as viewed in the He II 304\AA bandpass and the
enhanced 171\AA emission. In that bandpass, the prominence appears to extend
several megameters along the 171\AA horn where we observe co-spatial,
co-temporal 304\AA and 171\AA emission dynamics. We present these observations
as evidence of the magnetic and energetic connection between the prominence and
the cavity. Further modeling work is necessary to explain the physical source
and consequences of these events, particularly in the context of the
traditional paradigm: the cavity is under dense because it supplies mass to the
over dense prominence.
