Fermi large area telescope observations of the cosmic-ray inducedγ-ray emission of the Earth’s atmosphere

A A Abdo,F Piron,P Spinelli,M Kerr,G Godfrey,S Buson,D Parent,Y Uchiyama,J E Grove,A P Waite,C Meurer,T J Johnson,S Germani,T Ohsugi,M.-H Grondin,S Murgia,M N Lovellette,M Pesce-Rollins,M Kuss,J E Mcenery,E Charles,M S Strickman,A Bouvier,M Ziegler,J Kataoka,R Bellazzini,E Nuss,P L Nolan,P F Michelson,E Orlando,A Brez,F De Palma,J Bregeon,C Cecchi,D F Torres,M Ackermann,N Kawai,G Barbiellini,J Ballet,G H Share,T Ylinen,P Wang,A Y Rodriguez,A Makeev,C Favuzzi,I V Moskalenko,I A Grenier,C Monte,F Giordano,P Lubrano,W B Focke,A Reimer,D Dumora,V Vasileiou,K Bechtol,J G Thayer,P S Drell,B M Baughman,D A Smith,N Omodei,J F Ormes,E Hays,P Fusco,A Morselli,J M Casandjian,B L Winer,R E Hughes,J Cohen-Tanugi,R Dubois,B Giebels,L Guillemot,Ö Çelik,W N Johnson,S Funk,C Sgrò,J B Thayer,G Spandre,L Latronico,L Tibaldo,W Mitthumsiri,J Chiang,F Gargano,S J Fegan,A Okumura,M E Monzani,J Conrad,B Berenji,N Vilchez,A S Johnson,P M Saz Parkinson,E Bonamente,G A Caliandro,S W Digel,P A Caraveo,E D Bloom,A W Borgland,S Rainò,T H Burnett,T Glanzman,K S Wood,M Ajello,E Do Couto E Silva,N Gehrels,R Buehler,J Knödlseder,M Roth,Y Fukazawa,P D Smith,R Claus,T A Porter,D Bastieri,H Takahashi,D Horan,V Vitale,P Fortin,H Katagiri,D J Suson,M N Mazziotta,E J Siskind,B Lott,G Tosti,M Frailis,D J Thompson,A Chekhtman,F Loparco,A Sander,S Guiriec,C Farnier,A Tramacere,R Rando,W B Atwood,T Reposeur,N Giglietto,T Mizuno,M Brigida,S Ciprini,J P Norris,T Kamae,M Razzano,R A Cameron,D Paneque,V Pelassa,F Longo,Luca Baldini ,H F-W Sadrozinski ,J Landé ,Pascal Bruel ,G Jøhannesson ,T Usher ,M Pepé ,Leon Rochester ,M Lemoine‐Goumard ,J Panetta ,Takaaki Tanaka

doi:10.1103/physrevd.80.122004

Abstract

We report on measurements of the cosmic-ray induced gamma-ray emission of Earth's atmosphere by the Large Area Telescope onboard the Fermi Gamma-ray Space Telescope. The LAT has observed the Earth during its commissioning phase and with a dedicated Earth-limb following observation in September 2008. These measurements yielded 6.4 x 10^6 photons with energies >100MeV and ~250hours total livetime for the highest quality data selection. This allows the study of the spatial and spectral distributions of these photons with unprecedented detail. The spectrum of the emission - often referred to as Earth albedo gamma-ray emission - has a power-law shape up to 500 GeV with spectral index Gamma = 2.79+-0.06.

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