A 3-Year Sample of Almost 1,600 Elves Recorded Above South America by the Pierre Auger Cosmic-Ray Observatory

THE PIERRE AUGER COLLABORATION.; S. J. SCIUTTO

Earth and Space Science

Wiley - AGU

Lugar: Washington; Año: 2020 vol. 7 p. 1 - 17

Elves are a class of transient luminous events, with a radial extent typically greater than250 km, that occur in the lower ionosphere above strong electrical storms.We report the observation of1,598 elves, from 2014 to 2016, recorded with unprecedented time resolution (100 ns) using thefluorescence detector (FD) of the Pierre Auger Cosmic-Ray Observatory. The Auger Observatory is locatedin the Mendoza province of Argentina with a viewing footprint for elve observations of 3 · 106 km2,reaching areas above the Pacific and Atlantic Oceans, as well as the Córdoba region, which is known forsevere convective thunderstorms. Primarily designed for ultrahigh energy cosmic-ray observations, theAuger FD turns out to be very sensitive to the ultraviolet emission in elves. The detector features modifiedSchmidt optics with large apertures resulting in a field of view that spans the horizon, and year-roundoperation on dark nights with low moonlight background, when the local weather is favorable. Themeasured light profiles of 18% of the elve events have more than one peak, compatible with intracloudactivity. Within the 3-year sample, 72% of the elves correlate with the far-field radiation measurements oftheWorld Wide Lightning Location Network. The Auger Observatory plans to continue operations until atleast 2025, including elve observations and analysis. To the best of our knowledge, this observatory is theonly facility on Earth that measures elves with year-round operation and full horizon coverage.