We report here for the first time about the registration of an extraordinary high flux of low-energy neutrons generated during thunderstorms. The measured neutron count rate enhancements are directly ...connected with thunderstorm discharges. The low-energy neutron flux value obtained in our work is a challenge for the photonuclear channel of neutron generation in thunderstorm: the estimated value of the needed high-energy γ-ray flux is about 3 orders of magnitude higher than that one observed.
Problems associated with observations and interpretation of the physical mechanisms underlying the generation of hard electromagnetic radiation from lightning discharges are considered. A review of ...modern problems of understanding the nature of atmospheric flashes of gamma radiation from the Earth’s atmosphere is given. The results of orbital observations, in particular, on the
Vernov
satellite, are analyzed. The possibilities of orbital observations of atmospheric gamma-ray flashes on CubeSat spacecraft are discussed, and a description of the recording equipment is given. The technique of a laboratory experiment with long sparks, which simulates electrical discharges in thunderclouds, is considered.
We report the observation results of the hard radiation flashes which accompanied the lightning discharges above the mountains of Northern Tien Shan. Time series of the counting rate intensity, ...numerical estimations of absolute flux, and energy distribution of accelerated electrons and of (20−2000) keV gamma rays were obtained at the height of 3700 m a. s. l., immediately within thunderclouds, and in closest vicinity (≲100 m) to discharge region. Two different kinds of radiation emission events are presented here: a relatively prolonged rise of gamma ray intensity with minute-scale duration (the thunderstorm ground enhancement, TGE) which has preceded a negative field variation, and a short sub-millisecond radiation burst, which accompanied a close lightning discharge in thundercloud. It was revealed also an indication to positron generation in thunderclouds at the time of gamma ray emission, as well as modulation of the neutron counting rate in Tien Shan neutron monitor which was operating at a (1.5–2) km order distance from the region of lightning development.
•Emissions of hard radiation were studied in vicinity to atmospheric discharge.•The spectra of detected gamma rays are compatible with the runaway breakdown model.•Accelerated electrons were detected immediately within thundercloud.•It was revealed an indication to positron production in thundercloud.•Electric field of thundercloud modulated the counting rate in a neutron monitor
Simultaneous registration of electromagnetic emission generated by atmospheric lightning discharges in the radio-frequency (f = 0.1–30 MHz), infrared (λ = 610–800 nm), ultraviolet (λ = 240–380 nm), ...and in the soft energy gamma-radiation (Eγ = 0.1–4 MeV) ranges of electromagnetic spectrum was made synchronously in mountain conditions with complex detector system of the Tien Shan High-Mountain Cosmic Ray Station. We discuss preliminary results of these measurements and perspectives of future application of the multispectral investigation technique to study of the effects of thunderstorm activity.
•Different atmospheric discharge emissions were investigated simultaneously.•Modified set of equipment was used at Tien-Shan Station during thunderstorms.•Radio, optic (UV and IC) and soft energy gamma-radiation were registered.
The electric state of the near-surface atmosphere up to a height of 400 m is investigated using a tethered balloon with a measuring platform and a ground-based information-measuring complex of the ...Borok middle-latitude geophysical observatory. For the first time, measurements were taken simultaneously for vertical profiles of the atmospheric electric field, polar electrical conductivities, size distribution of aerosol particles, and the volume activity of radon, which have allowed estimating the average values and variability of the space charge density and conduction current in the atmosphere. The height dependence of the electric potential with respect to the Earth’s surface and electrical resistance of the near-surface atmospheric column under different conditions of the temperature stratification is studied.
Energetic radiation during thunderstorms is studied. The possibility to identify the high-energy lightning emission in the 10 s monitoring mode is demonstrated. Simultaneous measurements of gamma-ray ...emission, high-energy electrons, and neutron radiation in the triggering mode are fulfilled. Energy spectra of gamma emission and electrons are obtained. The intensity both of electrons and gamma rays in lightning discharge prevail the background emission by 1.5 to 2 orders of magnitude.
The time structure of neutron count rate enhancement during thunderstorm is studied. The enhancements take place during the time of atmospheric discharge. Significant part of neutrons is emitted in ...short bursts (200–400μs). Sometimes the emission is well correlated over the space scale 1km. Short burst width enables us to suppose that neutrons are generated mainly in a dense medium (probably soil).
•We study the neutron flux during thunderstorms with 0.2ms time resolution.•Neutrons are observed during atmospheric discharges as short 0.2–0.4ms bursts.•We suppose that neutrons are generated mainly in a dense medium, probably soil.
The results of simultaneous radio and gamma emission measurements during thunderstorms are presented. A gamma detector situated at the height 3840 m and two radio detectors of Tien-Shan Mountain ...Scientific Station (altitude 3340 m) registered intensive gamma flashes and radio pulses during the time of lightning initiation. The radio-gamma correlation grows abruptly at the initial moment (a few hundred microseconds), and the correlation coefficient reaches 0.9-0.95. The gamma-energy spectrum measured during lightning initiation is close to the characteristic spectrum of runaway breakdown. Radio pulses observed at the same time have highest amplitudes. Combined observation of gamma and radio emissions confirm the conception of lightning initiation due to multiple simultaneous electric discharges at hydrometeors stimulated and synchronized by low-energy electrons generated in the runaway breakdown process.
The observational evidence of RB-EAS discharge in a thunderstorm atmosphere is presented. After RB-EAS discharge we name a discharge of a special type developing due to the runaway breakdown (RB) ...mechanism while an extensive atmosphere shower (EAS) passes through a thundercloud electric field. The observations were fulfilled at the Tien-Shan Mountain Cosmic Ray Station. The widely spread system of oscillation detectors, the special EAS trigger array and the HF radio interferometer were used for measurements.
A series of features of the spectral characteristics of thunderstorm-cloud field perturbations is specified on the basis of long-term ground-based measurements of the electric field at remote ...locations. A significant increase in the spectral density of the electric-field variations during the thunderstorm has been observed. Maximum increase due to the pulsed field component, which is related to the lightning discharges, is observed in the fluctuation-period range from tens of seconds to several minutes. A significant increase is also observed in the range 0.5–1.5 mHz (10–30-min periods) in which the spectral density is increased by more than a factor of 10
4
, whereas the increase factor at the lower frequencies is equal to 100 (about 10 times for the field). Quasimonochromatic components (with 10–20-min periods) in the frequency fluctuation spectra of an electric field of the powerful thunderstorm clouds, which drift by frequency at the cloud initiation, maturity, and dissipation stages are found. It is shown that presentation of the sequence of the pulsed field perturbations related to the discharges in the form of a pulse flow with independent intervals (Poisson flow) agrees with the form of the fluctuation spectrum of the observed field and leads to an estimate of 10 s for the average relaxation (regeneration) time of the field in the thunderstorm-cloud vicinity after the discharge.
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