  Approximately 0.01 % of all Si IV 1394 A spectra sampled in 2013 and 2014 by
the Interface Region Imaging Spectrograph (IRIS) have IRIS burst profiles.
However, these events are not evenly distributed across datasets with 19.31 %
of these spectra being identified in only six rasters. Here, we investigate
five of these six datasets, to understand why they contain so many IRIS burst
profiles. This research will help guide future targeted analyses of IRIS
bursts. We analyse five datasets sampled by the IRIS satellite, studying both
Si IV 1394 A spectra and 1400 A filter slit-jaw imager (SJI) data. IRIS burst
profiles are identified through the use of an automated algorithm.
Additionally, we study co-spatial line-of-sight photospheric magnetic field
maps sampled by the Solar Dynamics Observatory's Helioseismic and Magnetic
Imager (SDO/HMI) instrument. The majority of identified IRIS burst profiles
(12401 out of 13904) found in the five datasets analysed here were localised to
seven small regions in the time-distance domain (temporal durations of <4 hours
and spatial lengths of <12" along the slit). The SJI data co-spatial to these
regions contained long-lived or repetitive compact brightenings, matching the
defined properties of UV bursts, which remained close to the IRIS slit
throughout their evolutions. The IRIS burst profiles were not limited to the
brightest pixels in the fields of view (FOVs) nor did they comprise the
majority of bright (>500 DN/s) pixels. These IRIS burst profiles occurred
co-spatial to evolving (e.g. cancelling) opposite polarity magnetic fields
where magnetic reconnection is thought to be possible. More than 10 % of the
IRIS burst profiles identified during the entirety of 2013 and 2014 are
contained in just seven small regions in the time-distance domain where
long-lived (lifetimes >10 minutes) or repetitive UV bursts occurred along the
axis of the IRIS slit.
