Reply to “Comment on ‘Long lasting low energy thunderstorm ground enhancements and possible Rn-222 daughter isotopes contamination’”

To identify the role of the gamma radiation from radon progenies in the long lasting thunderstorm ground enhancement (TGE) flux, a differential energy spectrum was measured with various spectrometers, including a precise $3^{\prime \prime }\times 3^{\prime \prime }$ NaI(Tl) spectrometer from ORTEC (FWHM $\sim 7.7\%$ at 0.6 MeV). Measurements demonstrate that radon progenies radiation significantly contribute to the winter enhancements in the energy range below 0.3–2 MeV. However, performed Monte Carlo simulations and observation of TGEs with plastic scintillators of various thickness and energy thresholds show that TGEs originate in intracloud electric fields. Recent registration of gamma glows by spectrometers located on board aircraft flying at 12–20 km altitude also confirms an “electric” nature of particle flux enhancements.

Figure 1

Energy spectra of the natural gamma radiation measured before the enhancement of count rate and during the enhancement. Bottom: energy spectrum of the “pure” signal obtained by extracting the background sample from the $\text{signal}+\text{background}$ one.

Figure 2

Selected TGE events of 2018. Bottom: one-minute time series of count rate of first NaI crystal from the Aragats NaI network. Middle: disturbances of near surface electric field measured by the EFM-100 electric mill located on the roof of MAKET experimental hall. Top: outside temperature and dew point measured by Davis automatic weather station located on the roof of same building.

Figure 3

One-minute time series of the maximal energies of the recovered differential energy spectra with NaI network (4 Na crystals were used).

Figure 4

Cumulative distribution of the one-minute maximal energies corresponding to TGE events depicted in Fig. 1.