We analyse the long lived radionuclide data (C-14, Be-10 and Cl-36) in tree rings and Greenland ice cores referred to the 660 BC event. The hypotheses of solar superflare impact on the atmosphere and Solar system collision with small sized dense interstellar cloud are considered. Decisive role in clarifying the situation is the experimental data on other isotope content available in ice for the periods under discussion. The data on Be-10 and (3)6(C)l (GRIP and NGRIP stations in Greenland) during the 660 BC event favour the second hypothesis. Various assumptions on the relationship between isotope production and deposition rates in the atmosphere are considered.

This paper describes a piezoelectric method for measuring the density and mass of ejecta from the free surface of a condensed material upon arrival of a shock wave at it and the use of this method at the Institute of Physics of Explosion (Institute of Experimental Physics of the Russian Federal Nuclear Center, Sarov). Piezoelectric sensor designs and methods of recording and signal processing are presented. Results of measuring the density and mass of ejecta using piezoelectric sensors, radiography, protonography, and the method of indicator foils are compared.

The high-altitude track of the rates of production of cosmogenic isotopes 14С, 10Be and 36Cl in the Earth’s atmosphere under the action of galactic cosmic rays is calculated using different intranuclear cascade models in the GEANT4 environment. Inferences based on these models are discussed in comparison to the available experimental data on these isotopes.

We used the GEANT4 toolkit to simulate the altitude and latitude profiles of the production rate of C-14, Be-10 and Cl-36 radionuclides by the galactic cosmic ray (GCR) interactions in the terrestrial atmosphere at a varying geomagnetic field. We found that applying two intranuclear cascade models incorporated in GEANT4 (Binary Intranuclear Cascade, BIC, and Bertini Intranuclear Cascade, BERT) result in significantly different production rate values. We present the conclusions about the certain model relevance to the abundance of these isotopes in the surface fallout, ice-core records and lunar soil depth profile. Comparison of our simulations with the recent publication of Poluianov et al. (2016) shows a good agreement for C-14 (BIC) and Be-10 (BERT) and a definite by the factor 2-3 difference in the Cl-36 (BIC) atmospheric yield functions. Also, the mean level and amplitude of the Be-10 variations in polar ice from central regions of Antarctica and Greenland could be accounted for its tropospheric production by GCRs. The fallout rate of Cl-36 there can be explained assuming its additional input from the stratosphere. Significant additional variations of radionuclide sedimentation rate in polar regions may arise due to tropopause height changes even at a constant atmospheric production rate of the certain isotope.

Helical magneto-cumulative generator (MCG) powered from explosive piezogenerator (EPG) is the most compact device among modern sources having output energy of 1-10 kJ. EPG matches well MCG on nature of their operation and design parameters; they are simple in use and do not require transforming and switching devices. This paper presents the results of the work on creating an autonomous small energy source based on EPG and MCG. The energy on the piezogenerator output reaches ~25 J at the expense of double-sided shock loading of the EPG piezoceramic unit. The energy is transmitted to the helical MCG with the initial inductance of ~1000 μH. Constructively, the energy source is made both in the form of a monoblock of ~2 dm 3 volume and in the form of two separate units, connected with high-voltage cable.

The production of the cosmogenic radionuclides 14C, 10Be, and 36Cl in the Earth’s atmosphere under the action of powerful impulsive proton and gamma-ray events (superpowerful solar flares and Galactic gamma-ray bursts) is considered. The possible “isotopic footprint” in natural archives (the concentrations of these isotopes in dated polar ice cores and annual tree rings) has been calculated by taking into account geophysical processes. The results obtained have been applied to analyzing the anomalous increase in the concentration of radiocarbon measured in tree rings dated 774–775 AD. Arguments for the fact that the most likely cause of this increase is the high-energy emission from a Galactic gamma-ray burst are adduced.

A study of long-term solar variability reflected in indirect indices of past solar activity leads to stimulating results. We compare the statistics of intervals of very low and very high solar activity derived from two cosmogenic radionuclide records and look for consistency in their timing and physical interpretation. According to the applied criteria, the numbers of minima and of maxima are 61 and 68, respectively, from the 10Be record, and 42 and 46 from the 14C record. The difference between the enhanced and depressed states of solar activity becomes apparent in the difference in their statistical distributions. We find no correlation between the level or type (minimum or maximum) of an extremum and the level or type of the predecessor. The hypothesis of solar activity as a periodic process on the millennial time scale is not supported by the existing proxies. A new homogeneous series of 10Be measurements in polar ice covering the Holocene would be of great value for eliminating the existing discrepancy in the available solar activity reconstructions.

We suggest an explanation of a sharp increase in the abundance of cosmogenic radiocarbon found in tree rings dated AD 775. The increase could originate from high-energy irradiation of the atmosphere by a Galactic gamma-ray burst. We argue that, unlike a cosmic ray event, a gamma-ray burst does not necessarily result in a substantial increase in long-lived 10Be atmospheric production. At the same time, the 36Cl nuclide would be generated in the amounts detectable in the corresponding ice-core samples from Greenland and Antarctica. These peculiar features allow experimental discrimination of nuclide effects caused by gamma-ray bursts and by powerful proton events.

An explanation is offered for the impulsive increase in the concentration of cosmogenic radiocarbon in annual tree rings (Δ14C ∼ 12‰) from AD ≃775. A possible cause of such an increase could be the high-energy emission from a Galactic gamma-ray burst. It is shown that such an event should not lead to an increase in the total production of 10Be in the atmosphere, as distinct from the effect of cosmic-ray fluxes on the atmosphere. At the same time, the production of an appreciable amount of 36Cl, which can be detected in Greenland and Antarctica ice samples of the corresponding age, should be expected. This allows the effects caused by a gamma-ray burst and anomalously powerful proton events to be distinguished.

Helical magneto-cumulative generator (MCG) powered from explosive piezo-generator (EPG) is the most compact device among modern sources having output energy of 1-10 kJ. EPG matches well MCG on nature of their operation and design parameters; they are simple in use and do not require transforming and switching devices. The paper presents results of work on creating autonomous small energy source based on EPG and MCG. The energy on the piezogenerator output reaches ~25 J at the expense of double-sided shock loading of the EPG piezoceramic unit. The energy is transmitted to the helical MCG with the initial inductance of ~1000 μH. Constructively the energy source is constructed both in the form of a monoblock of ~2 dm 3 volume, and the form of two separate units, connected with high-voltage cable.

Abundance of the cosmogenic nuclide chlorine‐36 (36Cl) was measured together with the chloride (Cl−) concentration in different horizons of Quaternary permafrost samples collected from various types of ground ice in the northeastern part of Siberia. The 36Cl/Cl in 32 samples ranged in value from 2.4 × 10−14 to 1.4 × 10−12. Nonetheless, after a few extreme values were excluded, these 36Cl/Cl ratios provided a local permafrost chronometry. The general concordance of the modeled ages with geological expectations and other chronological methods supports the potential power of the proposed dating method. However, the large observed change in ratios from higher to lower values during the transition from Last Glacial Maximum to Holocene climatic conditions remains unexplained. An attempt to make use of the corresponding beryllium‐10 (10Be) absolute concentrations in the same samples failed because input of 10Be attached to particulate matter into permafrost is unknown. Further 36Cl/Cl serial measurements of modern precipitation and fossil ground ice are needed to refine this dating method into a practical tool with a clear protocol.

The method for dating permafrost based on the 36Cl long-lived cosmogenic isotope is proposed. The production of 36Cl in the atmosphere and lithosphere under the action of CRs is analyzed. It has been indicated that the 36Cl/Cl isotopic ratio measured in ice is the measure of ice age. The results of permafrost sample dating with regard to the in situ production are presented. The method dating limit (2 Ma) has been calculated.

The cosmic ray flux through the atmosphere at different levels of solar activity is simulated. The Geant program package has been used to determine the atmospheric zones where the maximal contrast of the released ray energy originates between the periods of solar minimum and maximum. The geographic coordinates and altitudes of these zones have been calculated. The results can be used to search for statistical correlations between the solar activity variations and dynamics of atmospheric transparency.