Measurements of energy spectra of relativistic electrons and gamma-rays from avalanches developed in the thunderous atmosphere with Aragats Solar Neutron Telescope

Abstract

Aragats solar neutron telescope (ASNT) is a unique instrument allowing to measure the energy spectra of electrons accelerated and multiplied in the strong electric fields of the atmosphere. We describe the instrument setup, its operation condition, software, and hardware triggers. We present energy spectra of a very large thunderstorm ground enhancement (TGE) event observed on 6 October 2021. The detector response function, algorithm to recover energy spectra from the energy release histograms also are presented. The spectra recovery procedure is verified by simulation of the response function of the SEVAN detector, operating nearby ASNT. SEVAN is a stacked 3 layered detector, interlayered by lead filters registering both charged and neutral species of cosmic rays. The simulated and measured count rates of all 3 layers of the SEVAN detector show good agreement within 20%.

Structure of thunderstorm ground enhancements

“…Thus, it will be very difficult, to disentangle the 0.5% fraction during the energy recovery procedure. We need at least a few percent shares of electron candidates to start a rather complicated energy recovery procedure (see details in [6]). Nonetheless, we can see a notice of electron content in Fig.…”

“…During TGE such events are significantly enlarged compared with a fairweather count. The recovery of gamma ray and electron energy spectra is performed by solving the inverse problem of cosmic rays with a detailed simulation of the particle transport through the detector setup, including the selection of robust a-priory energy spectrum for calculating bin-to-bin migration (see details in [6]). In Fig.…”

TGE Electron Energy Spectra: Comment on “Radar Diagnosis of the Thundercloud Electron Accelerator” by E. Williams et al. (2022)

“…Thus, only if a strong accelerating electric field is well below 200 m can RREA electrons be registered by particle detectors, and their energy spectrum can be recovered. A detailed description of the Aragats solar neutron telescope (ASNT) and the method of energy spectra recovery can be found in (Chilingarian, Hovsepyan, Karapetyan, Sargsyan, & Chilingaryan, 2022) and in the next section, where we formulate the necessary condition for the revealing TGE electrons.…”

On the vertical and horizontal profiles of the atmospheric electric field during thunderstorms

“…Thus, in spite of rather different conditions of the NSEF disturbances, and different charge structures in the cloud above, the TGEs in both stations, registered by the same type of detectors share the same time. We checked the TGEs also by other particle detectors, on Aragats with solar neutron telescope [19], NaI spectrometer, 1 and 3 cm thick plastic scintillators, and in Nor Amberd with an array of Geiger counters located outdoors. The observed significances of peaks were compatible with the ones described above.…”