Cherenkov Flashes and Fluorescence Flares on Telescopes: New lights on UHECR Spectroscopy while unveiling Neutrinos Astronomy

Multi-GeV and TeVs gamma sources are currently observed by their Cherenkov flashes on Telescopes (as Magic, Hess and Veritas), looking vertically up into sky. These detectors while pointing horizontally should reveal also the fluorescence flare tails of nearby down-going airshowers. Such airshowers, born at higher (tens km) altitudes, are growing and extending up to lowest atmospheres (EeVs) or up to higher (few km) quotas (PeVs). These fluorescence signals extend the Cherenkov telescopes to a much higher Cosmic Ray Spectroscopy. Viceversa, as it has been foreseen [9] and only recently observed, the opposite takes place. Fluorescence Telescopes made for UHECR detection (as AUGER ones) may be blazed by inclined Cherenkov lights: less energetic, but frequent (PeVs) CR are expected to be often detected. Nearly dozens blazing Cherenkov at EeV should be already found each year in AUGER, possibly in hybrid mode (FD-SD, Fluorescence and/or Surface Detector). Many more CR events (tens or hundred of thousands) at PeVs energies should be blaze Cherenkov lights each year on the AUGER Fluorescence Telescopes. Their UV filter may partially hide their signals and they cannot, unfortunately, be seen yet in any hybrid mode. At these comparable energy the rarest UHE resonant antineutrino ν̄e + e interactions in air at MW 2 2me = 6.3 PeV energy, offer enhanced W Neutrino Astronomy showering at air horizon, at ∼ 90, while crossing deep atmosphere column depth or Earth (Ande) boundaries. However, AUGER FD are facing opposite way. An additional decay channel rises also (after resonant neutrino skimming Earth) via their secondary τ exit in air, by decay in flight via amplified showering: ν̄e + e → W − → ν̄τ + τ . Moreover, expected horizontal UHE GZK neutrinos ντ ν̄τ at EeVs energy, powered by guaranteed cosmogenic GZK [11,15], νμ ν̄μ flavor conversions (in cosmic distances), are also producing penetrating UHE EeV lepton taus that could sample, better and deeper than PeVs ones, the Earth skin. Such almost horizontal and up going tau showers, originated by UHE astronomical neutrino, may shower and flash by Fluorescence and/or Cherenkov diffused lights at Auger Sky in a few years (nearly three). Viceversa, at Hess, MAGIC and VERITAS Horizons, at tens or a hundred kilometer distances, the same up going τ τ̄ airshowers might rise via fluorescence. On axis they might blaze (rarely) as a Cherenkov flashes below the horizons, possibly correlated to BL Lac or GRB activity. Also UHE (1 − 0.1 EeV) GZK τ showering, can be observed upward once reflected onto clouds. The geomagnetic splitting may tag the energy as well as the inclined shower footprint as seen in a recent peculiar event in AUGER. Additional stereoscopic detection may define the event origination distance and its consequent primary composition, extending our understanding on UHECR composition.