The excitation functions in proton-induced reactions on natural gadolinium
nat
Gd(p,xn)
152,153,154,156,160
Tb were calculated for terbium isotopes, which are of interest from both scientific and ...application points of view. The calculations were performed in wide energy range of proton beam from the corresponding thresholds of reactions up to 70 MeV. The calculations were carried out using TALYS 1.96 and EMPIRE 3.2 nuclear reaction codes. Calculations have been done by different models inherent in these codes. The obtained results are compared with published experimental data. The discrepancies between experimental and theoretical data were discussed, which indicates the need to expand the experimental data base in order to improve the theoretical models.
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.
The Global atmospheric Electric Circuit (GEC) is a fundamental coupling network of the climate system connecting electrically disturbed weather regions with fair weather regions across the planet. ...The GEC sustains the fair weather electric field (or potential gradient, PG) which is present globally and can be measured routinely at the surface using durable instrumentation such as modern electric field mills, which are now widely deployed internationally. In contrast to lightning or magnetic fields, fair weather PG cannot be measured remotely. Despite the existence of many PG datasets (both contemporary and historical), few attempts have been made to coordinate and integrate these fragmented surface measurements within a global framework. Such a synthesis is important in order to fully study major influences on the GEC such as climate variations and space weather effects, as well as more local atmospheric electrical processes such as cloud electrification, lightning initiation, and dust and aerosol charging.
The GloCAEM (Global Coordination of Atmospheric Electricity Measurements) project has brought together experts in atmospheric electricity to make the first steps towards an effective global network for atmospheric electricity monitoring, which will provide data in near real time. Data from all sites are available in identically-formatted files, at both 1 s and 1 min temporal resolution, along with meteorological data (wherever available) for ease of interpretation of electrical measurements. This work describes the details of the GloCAEM database and presents what is likely to be the largest single analysis of PG data performed from multiple datasets at geographically distinct locations. Analysis of the diurnal variation in PG from all 17 GloCAEM sites demonstrates that the majority of sites show two daily maxima, characteristic of local influences on the PG, such as the sunrise effect. Data analysis methods to minimise such effects are presented and recommendations provided on the most suitable GloCAEM sites for the study of various scientific phenomena. The use of the dataset for further understanding of the GEC is also demonstrated, in particular for more detailed characterization of day-to-day global circuit variability. Such coordinated effort enables deeper insight into PG phenomenology which goes beyond single-location PG measurements, providing a simple measurement of global thunderstorm variability on a day-to-day timescale. The creation of the GloCAEM database is likely to enable much more effective study of atmospheric electricity variables than has ever been possible before, which will improve our understanding of the role of atmospheric electricity in the complex processes underlying weather and climate.
•We describe the first near global database (GloCAEM) for real time monitoring of atmospheric electric potential gradient (PG).•The largest single analysis of PG data from multiple datasets at geographically distinct locations is presented.•Approaches to selecting PG data for global electric circuit monitoring are discussed.•Recommendations are provided on the most suitable GloCAEM sites for the study of various scientific phenomena.
The role of free passage distance (FPD: the distance between the avalanche region and surface detectors) in influencing the relative numbers of energetic electrons and gamma rays in Thunderstorm ...Ground Enhancements (TGEs) is reconsidered and focuses on the contrast between long (>100 m) versus short (<100 m) FPDs, respectively. Estimates of FPD are based on information from published balloon soundings of the electric field, from published profiles of radar reflectivity in TGEs, and from analyses of Japan winter storms. All these data sources support typical values of FPD >100 m. Neither the shortcomings of present particle detectors in distinguishing electrons from gamma rays, nor the dominance of gamma rays over electrons, are sufficient evidence to deny the robust presence of Compton electrons at FDP values greater than 100 m that have also been shown in earlier simulations as well as the present Comment. Problems with having sustained electric fields of breakeven magnitude within 100 m of the Earth's surface (in relatively rare TGEs) are identified. The resolution of these problems, and the prominent nocturnal presence of these rare events, may possibly be explained by the descent of a strong field region in a collapsing storm, and by a low cloud base that intercepts and immobilizes fast corona ions, thereby preserving the intense electric field.
Plain Language Summary
Thunderstorms are capable of accelerating electrons to large energy by a process called electron runaway. This process is often confined to the cold portion of the thunderstorm at higher altitude where ice particles are available to separate electric charge to produce the necessary electric field, and where so‐called avalanche electrons are present. As a result, the high field region in the storm is removed from the ground where measurements of energetic radiation are usually undertaken to diagnose electron acceleration aloft. Gamma rays are produced when the energetic electrons are decelerated in coming in contact with heavy nuclei in a process called bremsstrahlung. Electrons unaided by strong field have short range in the atmosphere: tens of meters and less, whereas gamma rays have larger range (hundreds of meters). Accordingly, energetic electrons cannot be expected far (>200 m) below the high field region. One possible scenario for reducing this gap is the descent of strong field to near cloud base in a collapsing storm and the protection of field dissipation by the capture of small corona ions by cloud droplets. Evidence from several research areas in the literature is used to support the arguments in this paper.
Key Points
Energetic Compton electrons are an inevitable accompaniment of the gamma ray flux of Thunderstorm Ground Enhancements (TGEs) but in numbers too small to be readily distinguished from the gamma rays with typical detectors
The observations of avalanche electrons in TGEs is surprising, given the small free passage distance (FPD) (<50–100 m) required
One suggested scenario for creating small FPD is the lowering of negative charge in storm collapse and the capture of fast corona ions by cloud droplets
The formulation of the problem of surface control of an electroactive unidirectional multicomponent elastic wave propagation in an infinite piezoelectric waveguide over a finite time interval is ...discussed. Based on the conditions for conjugation of electromechanical fields on the surface of piezoelectric media, as well as on the nature of possible surface electromechanical effects, a variety of surface dynamic effects is considered through the components of the elastic displacement vector, the mechanical stress tensor, the tangential component of the electric field strength and the normal component of the electric field displacement. The possibility of setting the control problem in the case of three-component electroacoustic waves depending on the anisotropy of the piezoelectric material of the waveguide is studied. The anisotropy of a piezoelectric medium leads to the formulation of an initial-boundary mathematical problem for controlling the motion of a multicomponent system. The variety of surface actions leads to the formulation of heterogeneous initial-boundary mathematical problems with surface actions of the first kind, with surface actions of the second kind, as well as for the case of mixed surface actions. An invariant record of heterogeneous initial-boundary mathematical problems is proposed in the form of a system of inhomogeneous quasi-static electro-elasticity equations, with homogeneous boundary conditions and inhomogeneous conditions of the initial and final states
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Thunderstorm Ground Enhancements (TGEs) refer to correlated enhancements in surface electric field and gamma ray flux that are manifestations of electron runaway in the storm overhead. The electric ...field enhancements can be of positive or negative polarity. In this study, altitude‐resolved S‐band radar observations of graupel are used to demonstrate distinct differences in storm structure linked with these “positive” and “negative” TGEs. The physical interpretation rests on the well‐established temperature‐dependent tripole structure of thunderstorms, with the main negative charge of the tripole acting as an electron repeller. This interpretation is supported by case studies showing altitude‐stable convection, with shallow (deep) development linked with “positive” (“negative”) TGEs, and by case studies of collapsing storms that show upper dipole dominance early and lower inverted dipole dominance later when graupel particles descend from a colder to warmer temperature domain. In the case of many TGEs on Mt Aragats (3.2 km MSL), the temperature‐dependent altitude of downward electron acceleration and avalanching may be sufficiently distant (>500 m) from surface detectors that the energetic electrons (1–10 MeV) are not likely avalanche/runaway electrons. Instead, they are Compton‐scattered and pair‐produced electrons from bremsstrahlung gamma radiation emanating from the high‐field avalanche region aloft. These inferences are consistent with GEANT4 calculations that identify the physical origins of energetic electrons at the surface.
Key Points
Thunderstorm Ground Enhancements (TGEs) are indicative of downward electron acceleration within the storm and are manifest with both polarities of the electric field
Vertical development disclosed by RADAR is uniquely linked with "positive" and "negative" TGEs
These different vertical developments are attributed to a temperature‐dependent tripole structure of thunderclouds
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