Reconstruction of multiple ELVES with high time resolution and longer trace length at the Pierre Auger Observatory
Abstract:The Pierre Auger Observatory, located in Malargue (Argentina), is the largest facility (3000 km2 ) for the study of Ultra High Energy Cosmic Rays (E>1018 eV).
The four sites of the Fluorescence Detector (covering a field of view of 30x180 degrees each) are continuously observing the night sky with 100 ns time resolution and a space resolution below one degree. Since March 2013, a special trigger has been implemented to detect ELVES candidates with high efficiency, and since January 2014 the ELVES candidates are read with a modified DAQ scheme, which allowed to extend the trace lengths from 100 to 300 microseconds. This dedicated upgrade allows to observe the light emission from above the vertical of the causative lightning and to harvest a large sample of ELVES showing a double or even triple peak structure. In addition, a comprehensive review of the detector performance (trigger efficiency, time and angular resolution, altitude of the emission layer) during the data taking periods 2013 and 2014 is given.