Remarks on recent results on neutron production during thunderstorms

We analyze the neutron fluxes correlated with thunderstorm activity recently measured at mountain altitudes by the Tien-Shan, Tibet, and Aragats groups. We perform simulations of the photonuclear reactions of gamma rays born in the electron-gamma ray avalanches and calculate the expected count rates of the neutron detectors used by the three groups. We also present results of an independent experiment performed at the Nor Amberd high altitude research station in Armenia. Our analysis supports the Tibet and Aragats groups’ conclusions on the photonuclear nature of thunderstorm-correlated neutrons (directly in the neutron monitor and in the atmosphere). The photonuclear reactions of the gamma rays born in the electron-photon avalanches in the thunderstorm atmospheres interacting with the air atoms and with lead producer of a neutron monitor can provide neutron yield compatible with additional count of neutron monitors registered during thunderstorm ground enhancements.

Figure 1

Dependence of the neutron/gamma ray ratio on distance from the projection of the radiating region. Gamma rays are injected from an altitude of 4700 m according to energy spectrum measured during TGE on October 4, 2010. The detectors were located at 3200 m.

Figure 2

The energy dependence of the photon detection efficiency by the 60-cm-thick scintillator.

Figure 3

Nor Amberd multidirectional muon monitor arranged above and below two sections of the Nor Amberd Neutron Monitor; “bare” proportional counters are located on the third section of NANM.

Figure 4

The one-minute time series of count rates of upper and top layers of NANM and NANM.