This study analyzes near-infrared measurements of Io, Jupiter's moon,
observed over 170 nights from 2016 to early 2022 using the NASA Infrared
Telescope Facility (IRTF). During this period, seven new volcanic outbursts,
the most energetic volcanic events on Io, were discovered and characterized,
increasing the total number of observed outburst events from 18 to 25. We also
present simplified criteria for the thermal detection of an outburst, requiring
it to be both confined to a specific location of Io and above a threshold
intensity in the Lp-band (3.8 micron).
Our measurements use 2 to 5 micron photometry in eclipse, Jupiter
occultation, and reflected sunlight. In addition to extending the observational
dataset of Io's dynamic activity, these data provide insights into the temporal
and spatial distribution of outbursts on Io. Notably, all seven outbursts were
detected in Io's trailing hemisphere. These include Pillan Patera and a newly
discovered repeating outburst location at Acala Fluctus. We add these events to
the rare category of recurring outbursts, before which Tvashtar was the only
known example. We observed that another outburst at UP 254W decreased in
Lp-band intensity by a factor of two in 4.5 hours. In August 2021, Io exhibited
high volcanic activity when two powerful outbursts rapidly appeared,
propagating East. Our findings underscore IRTF's ongoing contributions to the
study of Io