Observation of neutron bursts associated with atmospheric lightning discharge

Abstract

Abstract. Neutron bursts with magnitude up to 10 9 were observed to be associated with atmospheric lightning discharge. where D is deuterium (1H 2) and He 3 is helium 3. To observe, if neutron emission <2 x 10 •ø is associated with lightning, a sensitive detector is required (the neutron emission is so low that it will make no statistically significant change in the atomic isotopes; therefore neutrons cannot be detected by anomalies in isotopes). We report here our effort to detect neutron bursts, associated with lightning, using a highsensitivity, large area neutron detecting system. The techniques used to record neutron emission data had an important difference. The laboratory at Gulmarg triggered their detection system by lightning-produced electromagnetic radiation and then recorded the neutron bursts. However, this technique has one pitfall. A large burst of cosmic ray may trigger lightning and also produce neutrons (by muons or spallation), which may be mistakenly assumed to be produced by lightning. Therefore our group at Mumbai recorded the bursts in untriggered mode and observed the burst neutron emission under different weather conditions. Since cosmic rays emission remains, on the average, the same for different weather conditions, therefore observing higher burst counts during lightning suggests neutron emission (either produced or associated with lightning). The two techniques are complimentary; therefore positive results by both the techniques confirm neutron emission is associated with lightning. Experimental SetupThe neutron detection system at Mumbai consisted of 16 BF 3 detectors of 0.05 m diameter, embedded in polyethylene neutron slowing-down material. The detector setup was housed in a professionally made, and tested, radio-frequency shielded enclosure. It could shield radio-frequency disturbances, radiated as well as conducted (through wire/cables) until 10 GHz by 110 dB. This provided the detection setup, immunity from radio-frequency interferences, which were even two orders of magnitude higher than interference produced during lightning. The burst counts, emitted in 100-/,rs time intervals, were continuously detected and stored.The number of neutrons (N) produced in a burst, associated with lightning, is given by Cn = K [exp(-qr)/d2]Nwhere Cn are counts recorded by detecting system during lightning and d is the distance between the detector and burst neutron source, which in this case is lightning. Exp(-qr) represents the attenuation of neutrons in moist atmosphere and 6867

Localization of the source of terrestrial neutron bursts detected in thunderstorm atmosphere

“…[15] Unfortunately comparison of the results of our simulations with the data of the experiments executed close to the sea level [Shyam and Kaushik, 1999;Kuzhevskij, 2004;Gusev et al, 2009] is impossible due to the lack of required details in these papers. The this same reason we did not simulate the neutron transport to a space based detector for comparison with the observations reported by Bratolyubova-Tsulukidze et al [2004].…”

“…In an experiment lasting three years and conducted with a refined configuration in a high mountainous region (the Himalayas, altitude z = 2743 m), Shah et al [1985] were able to measure statistically significant neutron flux increases above background and correlated with lightning electromagnetic pulses (EMP). Later statistically significant increases in neutron fluxes were observed near sea level during thunderstorms [Shyam and Kaushik, 1999;Kuzhevskij, 2004;Gusev et al, 2009] and terrestrial neutron flashes were also detected aboard an artificial satellite of the Earth [BratolyubovaTsulukidze et al, 2004].…”

“…Therefore to interpret the thunderstorm correlated neutron increases [Shah et al, 1985;Shyam and Kaushik, 1999;Kuzhevskij, 2004;Gusev et al, 2009] it is necessary to assume a tropospheric source of (g, n) reactions. This is the case because the hard g rays were observed to be associated with tropospheric sources [cf., e.g., Eack et al, 1996;Chubenko et al, 2000;Torii et al, 2002;Dwyer et al, 2004;Tsuchiya et al, 2007Tsuchiya et al, , 2009, and references therein].…”

“…[4] Absorption of neutrons in dense lower layers of the atmosphere is so strong that the predicted values of neutron yield N n in stratospheric discharges, even in the field of large thundercloud charges, are insufficient to account for the increases in neutron fluxes observed on the Earth's surface [Shah et al, 1985;Shyam and Kaushik, 1999;Kuzhevskij, 2004;Gusev et al, 2009] by g emission in the stratosphere [Babich, 2006Babich and RousselDupré, 2007]. Assuming a source of g emission responsible for (g, n) reactions located in the stratosphere, large delay times of neutron arrival at the detector relative to the lightning EMP t del , detected by Shah et al [1985], can be explained, but it is impossible to account for t del ≤ 100 ms [Babich, 2006Babich and Roussel-Dupré, 2007].…”

“…Therefore, to localize the neutron source altitudes, we carried out numerical simulations of volumetric photonuclear source located in the troposphere (thundercloud) and neutron transport from various altitudes to the altitude of the detector location in the mountains [Shah et al, 1985] and to sea level [Shyam and Kaushik, 1999;Kuzhevskij, 2004;Gusev et al, 2009].…”