Thunderstorm ground enhancements (TGEs) comprise large particle fluxes coming from the clouds that usually coincide with thunderstorms. Most of TGEs observed at the Aragats research station in ...Armenia during the last ten years originated from “beams of the electron accelerator” operating in the thunderclouds above the research station. Observed TGEs contain high-energy electrons and gamma rays (as well as neutrons) and usually last a few minutes. Starting from 2014, we use particle detectors tuned for the registration of lower energies particles coming from thunderclouds (starting from 0.3 MeV). In 2016, we already noticed that TGEs measured by particle detectors with a low energy threshold demonstrated a drastically larger duration. The flux of the high-energy particles (with energies up to 40 MeV) lasts 1–10 min; the lowest ones (less than 3 MeV)-more than two hours. All intense TGEs contain a high-energy peak and a prolonged low-energy extension lasting 2–3 h. In the presented paper, we describe examples of long-lasting TGEs and discuss correlations of enhanced particle fluxes with disturbances of the electric field and with precipitation.
The study presented the relationship between sudden Natural Gamma Radiation (NGR) increases related to enhanced atmospheric electric fields. We pinpoint Thunderstorm Ground Enhancements (TGEs) as the ...primary source of abrupt and significant NGR spikes. These TGEs, which are transient, several-minute-long increases in elementary particle fluxes, originate from natural electron accelerators within thunderclouds. The more prolonged, yet less pronounced, increases in NGR, persisting for several hours, are attributed to the gamma radiation from radon progeny and enhanced positron fluxes. This radon, emanating from terrestrial materials, is carried aloft by the Near-Surface Electric Field (NSEF). To measure NGR at Aragats Mountain, we use an ORTEC detector and custom-built large NaI (Tl) spectrometers, employing lead filters to discriminate between cosmic ray fluxes and radon progeny radiation. Our analysis differentiates between radiation enhancements during positive and negative NSEF episodes. The resultant data provide a comprehensive measurement of the intensities of principal isotopes and positron flux during thunderstorms compared to fair weather conditions.
•We measure NGR at Mt. Aragats (3200 m height) during thunderstorms.•NGR was enhanced many times for minutes and ≈20% for hours.•Positive NSEF is 1.5 more effective than negative in enhancing NGR.•Atmospheric positron flux boosts twice during positive near-surface electric fields.•The negative aerosol share on Earth is larger than that of positive aerosols.
Natural gamma radiation is a crucial aspect of our environment that has significance in various fields, such as radiation protection and geological exploration. Understanding and monitoring natural gamma radiation levels for human safety and scientific purposes is essential. In this context, we discuss two new sources of natural gamma radiation: thunderstorm ground enhancements and enhanced radon progeny radiation in stormy weather. Both are associated with strong atmospheric electric fields. We measured enhanced natural gamma radiation in the energy range 0.3–3 MeV at positive and negative NSEF. We found that the positive NSEF is 1.5 times more effective than the negative one. Additionally, we demonstrated that positron flux is enhanced by 2.5 times more at positive NSEF compared with negative NSEF.
After introducing spectrometers with the energy threshold of 0.3 MeV the pattern of the thunderstorm ground enhancements (TGEs) observed on Aragats dramatically changed demonstrating multi-hour ...radiation. In the paper, we analyze comprehensive observations made on different time scales and energy ranges. A new model of TGE is discussed explaining much larger time of particle fluxes from clouds.
Employing large thunderstorm ground enhancements (TGEs) as a manifestation of the strong electric field in thundercloud we measure fluxes of almost all species of secondary cosmic rays to estimate ...the strength of the intracloud electric field. The modulation that electric field poses on charged particle flux gives a sizable change in count rate of detectors measuring high energy muon flux and inclined muon flux in the presence of a TGE. The muon stopping effect, observed by the particle detectors located at 3200 m altitude at Aragats Space Environmental Center (ASEC) implicates the abrupt decline of count rate of high energy muons (at vertical incidence with energies above 250 MeV and at inclined incidence with azimuth angle θ> 22° for lower energies). For the large TGE events (relative enhancement > 10% in SEVAN detector upper layer, registering low energy charged particles and electrons) muon count rate decreases down to 2-5% from the mean count rate measured before the TGE event. A simple model of shifting of the energy spectrum of particles entering the electric field was applied for the analysis of several events where the muon stopping (deceleration) effect has been observed. For the large TGE events that occurred during last decade the maximal potential drop of 350 MV was estimated. The most probable electric field strength for this event was found to be ∼2 kV/cm.
After having published the first thunderstorm ground enhancements (TGEs) catalog to explain long-lasting TGEs, we address here problems pertaining to TGE evolution (shape) and atmospheric conditions ...supporting the origination of the relativistic runaway electron avalanches. We also address the question of radon progeny gamma radiation and its contribution to overall TGE flux. We demonstrate that by using detectors with different energy thresholds we can identify and reliably separate both mechanisms of TGE origination. An analysis of measured energy spectra of TGEs reveals contributions of both processes to the TGE temporal evolution and shape. We also confirm the model of radon progeny radiation during a thunderstorm.
Recent studies of thunderstorm-related enhancements of fluxes of energetic radiation and particles at ground level suggest that removal of mid-level negative charge from the cloud by negative ...cloud-to-ground (-CG) lightning flashes or normal intracloud (IC) flashes serves to abruptly terminate those enhancements. However, it was not clear if the electron-accelerating electric field responsible for flux enhancements at ground was primarily between the main negative charge region and ground (produced due to the dominant effect of negative cloud charge) or between the mid-level negative and lower positive charge regions inside the thundercloud. Here, we report that these flux enhancements can be also abruptly terminated by inverted intracloud flashes and hybrid lightning flashes (inverted IC followed by negative CG). Based on the analysis of 13 events of these two types, we provide first evidence that the electric field between the mid-level negative and lower positive charge regions in the thundercloud can be responsible for the flux enhancements at ground level.
•Lightning discharges can influence the evolution of enhanced fluxes of energetic radiation and particles (TGEs).•TGEs can be abruptly terminated by inverted intracloud flashes (ICs) and by hybrid flashes (inverted IC followed by -CG).•Electron accelerator between main negative and lower positive cloud charge regions is capable of producing TGEs.
The problem of thundercloud electrification is one of the most difficult ones in atmospheric physics. The structure of electric fields in clouds escapes from the detailed in situ measurements; few ...balloon flights reveal these rather complicated structures. To gain insight into the problem of the charge structure of a thundercloud, we use new key evidence-the fluxes of particles from a thundercloud, the so-called thunderstorm ground enhancements-TGEs. TGEs originate from electron acceleration and multiplication processes in the strong electric fields in the thundercloud, and the intensity and energy spectra of electrons and gamma rays as observed on the Earth’s surface are directly connected with the atmospheric electric field. Discovery of long-lasing TGEs poses new challenges for revealing structures in the thundercloud responsible for hours-extending gamma ray fluxes. In the presented paper, we demonstrate that experimentally measured intensities and energy spectra of the “thundercloud particles” give clues for understanding charge structures embedded in the atmosphere. A rather short “runaway” process above the detector site, which is consistent with the tripole structure of the cloud electrification, is changing to a much less energetic emission that lasts for hours. Measurements of enhanced particle fluxes are accompanied by the simulation experiments with corsika and geant4 codes.
The natural electron accelerator in the clouds above Aragats high-altitude research station in Armenia operates continuously in 2017 providing more than 100 Thunderstorm Ground enhancements (TGEs). ...Most important discovery based on analysis of 2017 data is observation and detailed description of the long-lasting TGEs. We present TGE catalog for 2 broad classes according to presence or absence of the high-energy particles. In the catalog was summarized several key parameters of the TGEs and related meteorological and atmospheric discharge observations. The statistical analysis of the data collected in tables reveals the months when TGEs are more frequent, the daytime when TGEs mostly occurred, the mean distance to lightning flash that terminates TGE and many other interesting relations. Separately was discussed the sharp count rate decline and following removal of high-energy particles from the TGE flux after a lightning flash. ADEI multivariate visualization and statistical analysis platform make analytical work on sophisticated problems rather easy; one can try and test many hypotheses very fast and come to a definite conclusion allowing crosscheck and validation.
Experimental results obtained a few decades ago associate the knee with the bending of the light component (
p
and He), and are compatible with a rigidity-dependent cut-off at 3–5 PeV. On the ...contrary, new experiments obtained by arrays located at high altitudes indicate that the light component cuts off well below 1 PeV. We re-analyze the energy spectrum of light nuclei obtained by the MAKET-ANI experiment at Aragats Mt. in Armenia and put them in the context of new experimental evidence.
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