Parametrization and Characterization of Multiple ELVES at the Pierre Auger Observatory

ELVES are being studied since 2013 with the twenty-four FD Telescopes of the Pierre Auger Observatory, the world’s largest facility for the study of ultra-high energy cosmic rays, in the province of Mendoza (Argentina) exploiting a dedicated trigger and extended readout. Since December 2020, this trigger has been extended to the three High Elevation Auger Telescopes (HEAT), which observe the night sky at elevation angles between 30 and 60 degrees, allowing to study ELVES from closer lightning. The high time resolution of the Auger telescopes allows to do detailed studies on multi-ELVES. The origin of multi-ELVES is not yet fully understood, and can be studied by analysing the time difference(s) and the amplitude ratio(s)  between flashes as a function of the radial distance of lightning emission from the causative lightning. At least two, if not three, distinct models are needed to explain the geometry of multi-ELVES events. This contribution will review the frequency of each class of multi-ELVES and correlate them to data from ENTLN, WWLLN, and GOES databases.