Spectrum of Gamma Rays, Produced by the Runaway Electrons G.G. Karapetyan Alikhanian National Laboratory, Armenia

In electric field of thunderstorm, the electrons can be accelerated to great energies and produce radiation [1] [1] C.T.R. Wilson “The acceleration of betta-particles in strong electric fields such as those of thunder-clouds”, Proc.Cambridge Philos. Soc., v.22, , 1924

Terrestrial gamma-ray flashes (TGF) were discovered by satellite observations [2] -about 50 TGFs occur per day -they are ~0.1…10ms pulses, emitted from the top of thunder clouds -bremsstrahlung of accelerated electrons [2] G.J. Fishman et al “Discovery of intense gamma ray flashes of atmospheric origin” Science, v.264, , 1994

Theory of relativistic runaway electron avalanche (RREA) [3] [3] A.V. Gurevich et al, “Runaway electron mechanism of air breakdown and preconditioning during a thunderstorm”, Phys. Lett. A, 165, 463– 468, 1992.

Spectrums of RE were derived by MC simulations S (E)~exp(-E/7MeV) p=1atm [5] L.P. Babich et al, Geomag. Aeronomija,v 44, N5, pp ,2004

Cross section for bremsstrahlung of ultra relativistic electron [4] E>>mc 2, E 1 >> mc 2 and ћ  >> mc 2 mc 2 =0.51MeV [4] V.B. Berestecki et al “Relativistic Quantum theory of Field” 1968, p. 424

Spectrum of gamma rays

TGFs are well described by exp(-E/7MeV)/E

Ground based measurements of long duration gamma pulses (LDGP) [5] [5] M. Brunetti et al “Gamma-ray bursts of atmospheric origin in the MeV energy range”, Geoph.Res.Lett., v. 27(11) pp , 2000 Aragats measurements

Spectrums of TGF and LDGP

TGFLDGP Duration<10msDozens min DirectionUpward, Downward Source LocationAbove thunder cloud Beneath, inside thunder cloud Association with the lightning YesNo (?) SpectraExp(-E/7MeV)/E 0.1MeV<E<30MeV 1/E a, a=2.6…4.1 10MeV<E<50MeV TheoryYes (?)No Table 1

Questions, which have to be answered by theoretical modeling What is the mechanism underlying LDGP? Why LDGP were detected by ground based and newer by spacecraft detectors? How broken energy (~7MeV) is derived? Why it weakly depends on electric field? What is the maximal energy of LDGP quanta?