The first finite-difference time-domain model effectively showed that the energy density of some very low frequency EMPs was sufficient to heat the plasma at the base of the E-layer of the nighttime ionosphere and induce the fluorescence process of molecules (Taranenko et al., 1993). ( 1991, 1997) predicted quantitatively that ionospheric heating by electromagnetic pulses (EMPs) originating from lightning strokes would create a transient flash of light expanding radially faster than the speed of light. To the best of our knowledge, this observatory is the only facility on Earth that measures elves with year-round operation and full horizon coverage. The Auger Observatory plans to continue operations until at least 2025, including elve observations and analysis.

Within the 3-year sample, 72% of the elves correlate with the far-field radiation measurements of the World Wide Lightning Location Network.

The measured light profiles of 18% of the elve events have more than one peak, compatible with intracloud activity. The detector features modified Schmidt optics with large apertures resulting in a field of view that spans the horizon, and year-round operation on dark nights with low moonlight background, when the local weather is favorable. Primarily designed for ultrahigh energy cosmic-ray observations, the Auger FD turns out to be very sensitive to the ultraviolet emission in elves. , reaching areas above the Pacific and Atlantic Oceans, as well as the Córdoba region, which is known for severe convective thunderstorms. The Auger Observatory is located in the Mendoza province of Argentina with a viewing footprint for elve observations of We report the observation of 1,598 elves, from 2014 to 2016, recorded with unprecedented time resolution (100 ns) using the fluorescence detector (FD) of the Pierre Auger Cosmic-Ray Observatory. Elves are a class of transient luminous events, with a radial extent typically greater than 250 km, that occur in the lower ionosphere above strong electrical storms.

American Elves by John E. Roth