Investigating multiple ELVES and halos above strong lightning with the fluorescence detectors of the Pierre Auger Observatory

ROBERTO MUSSA; PIERRE AUGER COLLABORATION; MARIA G. NICORA

Conferencia; 38th International Cosmic Ray Conference (ICRC2023); 2023

ELVES are being studied since 2013 with the twenty-four FD Telescopes of the Pierre AugerObservatory, in the province of Mendoza (Argentina), the world’s largest facility for the studyof ultra-high energy cosmic rays. This study exploits 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 astudy of ELVES from closer lightning. The high time resolution of the Auger telescopes allowsus to upgrade reconstruction algorithms and to do detailed studies on multiple ELVES. The originof multiple elves can be studied by analyzing the time difference and the amplitude ratio betweenflashes and comparing them with the properties of radio signals detected by the ENTLN lightningnetwork since 2018. A fraction of multi-ELVES can also be interpreted as halos following ELVES.Halos are disc shaped light transients emitted at 70-80 km altitudes, appearing at the center of theELVES rings, due to the rearrangement of electric charges at the base of ionosphere after a stronglightning event.