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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
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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, 534-538, 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, 1313-1316, 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.
0.1
1
0.1 1 10 100 1000
Energy (MeV)
Dra
g Fo
rce
(MeV
/m)
Fion
Fbr
Ftotal=Fion+Fbr
h=3.2km
eE=0.3MeV/m
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.697-703,2004
1.E-05
1.E-04
1.E-03
1.E-02
1.E-01
1.E+00
1.E+01
1 10 100
Energy (MeV)
Spec
trum
of R
E (A
.U.)
exp(-E/7MeV)
MC simulation (Babich)
Cross section for bremsstrahlung of ultra relativistic electron [4]
E>>mc2, E1>> mc2 and ћ >> mc2 mc2=0.51MeV
[4] V.B. Berestecki et al “Relativistic Quantum theory of Field” 1968, p. 424
212ln
3214 2
12
21122
mc
EEEE
EEdrZd e
Spectrum of gamma rays
dEESddN )()(
dEESmc
EEE
N )(ln11)(2
2
43
)/exp()( 0EEES
Spectrum of gamma rays
dEEEmc
EEE
N )/exp(ln11)( 02
2
43
)/exp(1)( 0EN
1.E-01
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1 10 100
Energy (MeV)
Gam
ma
spec
trum
(A.U
.)
exp(-E/7)/E
exact
TGFs are well described by exp(-E/7MeV)/E
1.E+00
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
0.1 1 10 100Energy (MeV)
Gam
ma
spec
trum
(cou
nts/
(s*M
eV))
AGILEx1000 fit RHESSI
~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. 1599-1602, 2000
Aragats measurements
-5
0
5
10
15
20
25
14:30 15:00 15:30 16:00 16:30 17:00 17:30 18:00 18:30 19:00 19:30 20:00
21 May 2009 (UT)
(Cou
nts
%)
electrons and gammas neutrons
Spectrums of TGF and LDGP
1.E+01
1.E+02
1.E+03
1.E+04
1.E+05
1.E+06
1.E+07
1.E+08
0.1 1 10 100Energy (MeV)
Gam
ma
spec
trum
(1
/m^2
*min
*MeV
)
RHESSI Aragats 19 Sept Norikuraexp(-E/7MeV)/E Aragats 21 May
~1/E^3
~1/E^2.6
TGF LDGP
Duration <10ms Dozens min
Direction Upward,Downward
Downward
Source Location Above thunder cloud
Beneath, inside thunder cloud
Association with the lightning
Yes No (?)
Spectra Exp(-E/7MeV)/E0.1MeV<E<30MeV
1/Ea, a=2.6…4.110MeV<E<50MeV
Theory Yes (?) 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?