Spectra of the Thunderstorm Correlated Electron and Gamma-Ray Measured at Aragats Bagrat Mailyan and Ashot Chilingarian

TEPA , September , 2010, Nor Amberd, Armenia Particle acceleration in atmospheric electric fields Runaway Relativistic Electron Avalanche (RREA)

TEPA , September , 2010, Nor Amberd, Armenia Detectors of Aragats Space-Environmental Center Detectors located outdoor and indoor correspond to the various energy thresholds of measured particles. Indoor detectors also located under roof materials with different thicknesses. These detectors, sensitive to various energies, allow us to construct the energy spectrum of the additional particles.

TEPA , September , 2010, Nor Amberd, Armenia Recently 3 layers of 1 cm and 1layer of 3cm scintillating detectors are installed outdoors.

TEPA , September , 2010, Nor Amberd, Armenia Aragats Solar Neutron Telescope (ASNT) ASNT detects not only particle count rate, but also energy releases spectra in scintillators!

TEPA , September , 2010, Nor Amberd, Armenia Light attenuation in thick scintillators Chilingarian et al., 2007 Scintillator layersLight output (%)

TEPA , September , 2010, Nor Amberd, Armenia Reconstruction of the energy spectra of incident gammas The unfolding of the gamma ray spectrum above the roof of the MAKET building at altitude of 3250 m was made in the following way: A power spectrum with initial parameters randomly chosen from predetermined interval is generated; This spectrum is used to simulate traversal of gamma rays via roof and ASNT detector components to finally obtain simulated energy release spectrum; The obtained simulated spectrum is compared with experimental one; the discrepancy (quality function) and initial spectrum parameters are stored; If number of iterations is not fulfilled go to step 1.

TEPA , September , 2010, Nor Amberd, Armenia Reconstruction of the gamma spectrum of September 19, 2009 event The minimum of quality function corresponds to power index Electron contamination of gamma spectrum is taken into account.

TEPA , September , 2010, Nor Amberd, Armenia Electron contamination of gamma spectra and gamma contamination of electron spectra

TEPA , September , 2010, Nor Amberd, Armenia Construction of electron spectra of September 19, 2009 We correct the electron energy spectrum for the gamma-ray contamination. After the electron number correction for gamma contamination, 59472, 28268, and electrons were estimated to be detected by MAKET outdoor, MAKET indoor and SEVAN detectors respectively. According to calculations and simulations 4 types of detectors have energies approximately equal to 9, 12, 15, 18 MeV. Errors about 2 MeV, reflecting uncertainties in determination of the energy thresholds, are taken due to the complicated structure of roof substance To compare electron and gamma spectra, gamma differential spectrum was integrated.

TEPA , September , 2010, Nor Amberd, Armenia Electron and gamma ray spectra of September 19, 2009 event

TEPA , September , 2010, Nor Amberd, Armenia Reconstruction of the electron spectrum just below the thundercloud electric field We can assume that maximal energy of the RREA electrons can reach MeV. (Marisaldi et al., 2010) Taking into account the maximal energy of detected electrons and assuming that electrons lose 200 keV per meter of air, thundercloud altitude was estimated to be ~ m! By trying different trial spectra, evaluating the avalanche from 3380 till 3250 m and comparing each obtained spectrum with experimental one we have found the RREA spectrum, just below the thundercloud. The exponential index was found to be ~

TEPA , September , 2010, Nor Amberd, Armenia Reconstruction of the electron spectrum just below the thundercloud electric field

TEPA , September , 2010, Nor Amberd, Armenia Parameters of the fit for September 19 event

TEPA , September , 2010, Nor Amberd, Armenia Electron and gamma spectra of September 19, 2009 event

TEPA , September , 2010, Nor Amberd, Armenia Comparison with other events We have perform the same operations as for September 19 event to reconstruct the gamma spectra and obtain electron spectra of three smaller thunderstorm events. Gamma contamination of electron spectra are taken into account.

TEPA , September , 2010, Nor Amberd, Armenia May 21 event: More gammas than electrons

TEPA , September , 2010, Nor Amberd, Armenia July 9 event: No electrons only gammas

TEPA , September , 2010, Nor Amberd, Armenia August 26, 2010 event The energy thresholds were estimated to be 1.5, 4.5 and 7.5 MeV for upper, middle and lower detectors respectively.

TEPA , September , 2010, Nor Amberd, Armenia Comparison of the differential gamma spectra of the three events Intensity [#/sq.m.min.] for >7MeV gammasPower law index May July September August

TEPA , September , 2010, Nor Amberd, Armenia Comparison with gamma spectra calculated and measured with other groups According to simulations by J.R.Dwyer (2008), the RREA spectrum is independent on thundercloud electric field. The mean electron energy is ~7.3 MeV. Using Baksan data, Lidvansky and Khaerdinov (2009) assume 1000, 2000, 3000 m cloud height, to obtain 3 different values of the power spectra index from to to -4.36, for various events discussed in the paper. For instance, at October 11, 2003 the spectral indexes were estimated to be , -4.09, for 1000, 2000, 3000 m respectively. Tsuchiya et al., (2009) have simultaneously observed electrons and gammas spectrum extending up to 10 MeV on the top of the mountain Norikura, 2700 m above sea level. The RREA electrons source distance is estimated to be ~90m and spectral index of the gamma spectrum is ; no energy spectrum of electrons was presented.

TEPA , September , 2010, Nor Amberd, Armenia Conclusion For the first time we present the energy spectra of RREA electrons and gamma rays, using the variety of ASEC detectors including the enhanced possibilities of ASNT to measure energy releases in the thick scintillator. Gamma ray spectra are described by power law and electron spectra by exponential law. The intensities of additional particle fluxes for the discussed events are different. Electron/gamma ratio also varies for different thunderstorm events. There is an event without electron detections >9 MeV. Probably this is connected with thundercloud height.

TEPA , September , 2010, Nor Amberd, Armenia Thank you for attention! Acknowledgements The work was partially supported by the grant No. CRDF-NFSAT-SCS MES RA ECSP-69/A-27