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Lightning was detected by Voyager 2 at Uranus and Neptune, and weaker electrical processes also occur throughout planetary atmospheres from galactic cosmic ray (GCR) ionisation. Lightning is an indicator of convection, whereas electrical processes away from storms modulate cloud formation and chemistry, particularly if there is little insolation to drive other mechanisms. The ice giants appear to be unique in the Solar System in that they are distant enough from the Sun for GCR-related mechanisms to be significant for clouds and climate, yet also convective enough for lightning to occur. This paper reviews observations (both from Voyager 2 and Earth), data analysis and modelling, and considers options for future missions. Radio, energetic particle and magnetic instruments are recommended for future orbiters, and Huygens-like atmospheric electricity sensors for in situ observations. Uranian lightning is also expected to be detectable from terrestrial radio telescopes.

The work is devoted to the study of the possibility of manifestation of the effects of dynamic diffraction of coherent X-ray radiation of relativistic electrons in a periodic layered medium with three layers in a period. Coherent X-ray radiation is considered as a sum of parametric X-ray radiation and diffracted transition radiation. The dynamic theory of coherent X-ray relativistic electrons in the periodic layered medium with three layers in a period is developed. Within the framework of the two-wave approximation of the dynamic theory of diffraction, expressions in real form are obtained that describe the spectral-angular and angular density of radiation. The possibility of manifestation of the effects of dynamic diffraction of coherent X-ray radiation is investigated. The effect of asymmetry of the electron field reflection relative to the target surface on the spectral-angular densities of parametric X-ray and diffracted transition radiation is shown. The possibility of a bright manifestation of the effect of anomalous photoabsorption in parametric X-ray radiation in the considered three-layer structure is shown. This effect is analogous to the well-known Borrmann effect for X-rays in a single crystal.

Properties of type III and type IIIb bursts in the frequency band of 8 – 80 MHz observed by the radio telescopes Ukrainian Radio Interferometer of NASU-2 (URAN-2) (Poltava) and Giant Ukrainian Radio Telescope (GURT) (Kharkiv) during the Parker Solar Probe (PSP) perihelion in April 2019 are discussed. These correspond to those that were observed by PSP at frequencies <19 MHz. We analyze dependencies of drift rates and durations on frequency for these bursts. We show that drift rate dependencies on frequency agree well with those derived from the Newkirk corona if source velocities are between 0.17 and 0.2 c for both type IIIb bursts and type III bursts under the assumption that the first ones are fundamentals and the second ones are their harmonics. However, all observational dependencies are flatter in comparison with the dependencies for a Newkirk corona. We assume that this can be related with coronal temperature decreasing at heliocentric distances from 1.35 to 6.5 solar radii. Duration dependencies of type IIIb and type III bursts on frequency in the range of 10 – 70 MHz are also obtained. We note that the durations and drift rates of type III bursts as well as their dependencies on frequency differ essentially from those for type IIIb bursts.

Radio astronomy at decameter wavelengths is currently undergoing very active development. Large-scale, new generation low-frequency radio telescopes are being constructed and already used in many countries around the world. As before, the largest, most sensitive, and most versatile telescope at decameter wavelengths is the Ukrainian UTR-2 radio telescope operating at 8–32 MHz, which has an effective area of more than 10 5 m 2 and an angular resolution of about 0.5◦, as well as the URAN interferometric system based on the UTF-2. Many studies that have been carried out on these facilities have been based on important results and far-sighted predictions of Shklovskii. These include, in particular, studies of dynamical spectra and the brightness distributions of the sporadic and quiescent decameter radio emission of the hot solar corona, complex, broadband radio spectroscopy of the interstellar medium, and multi-frequency monitoring of secular decreases in the flux densities of supernova remnants. The coordinated use of highly effective existing and newly constructed radio telescopes joined into ground networks, as well as specialized space missions, are opening new prospects for low-frequency radio astronomy.

An event on 14 June 2012, observed with the radio telescopes UTR-2 (Kharkov, Ukraine), URAN-2 (Poltava, Ukraine), and NDA (Nançay, France) during a joint Summer campaign, is analyzed and discussed. The high solar activity resulted in a storm of spikes, and a storm of Type III bursts, Type IIIb bursts, and a Type IV burst observed in the decameter band. During the observed time interval, the average flux of radio emission changed twice. Using spikes as a tool for diagnostics of plasma parameters, we followed variations of the coronal temperature and the coronal magnetic field in the observed time interval. Thus, in frames of the model described in this article the observed decameter spikes’ durations of 0.3 – 1 seconds correspond to the coronal plasma temperatures of ≈ 0.1 – 0.6 × 10 6 K . At the same time the spikes’ frequency bandwidths of 25 – 80 kHz give us the magnetic-field value of about 2 G.

The results of experimental study of structural integrity destruction of lithium-thionyl chloride batteries are provided in the article. The research methodology in non-standard situations was realized using the mechanical damage of the battery body integrity by impact of metal rod on the battery body. Battery charge impact assessment was held during the research process. Pressure change dependences in manometric bomb in the moment of explosion of lithium-thionyl chloride batteries are presented in the paper.

We analyze and discuss the properties of decameter spikes observed in July – August 2002 by the UTR-2 radio telescope. These bursts have a short duration (about one second) and occur in a narrow frequency bandwidth (50 – 70 kHz). They are chaotically located in the dynamic spectrum. Decameter spikes are weak bursts: their fluxes do not exceed 200 – 300 s.f.u. An interesting feature of these spikes is the observed linear increase of the frequency bandwidth with frequency. This dependence can be explained in the framework of the plasma mechanism that causes the radio emission, taking into account that Langmuir waves are generated by fast electrons within a narrow angle θ ≈13 ∘  – 18 ∘ along the direction of the electron propagation. In the present article we consider the problem of the short lifetime of decameter spikes and discuss why electrons generate plasma waves in limited regions.

We report on the results of observations of a type IV burst made by the Ukrainian Radio interferometer of the Academy of Sciences (URAN-2) in the frequency range 22 – 33 MHz. The burst is associated with a coronal mass ejection (CME) initiated by a behind-the-limb active region (N05E151) and was also observed by the Nançay Decameter Array (NDA) radio telescope in the frequency band 30 – 60 MHz. The purpose of the article is the determination of the source of this type IV burst. After analysis of the observational data obtained with the URAN-2, the NDA, the Solar-Terrestrial Relations Observatory (STEREO) A and B spacecraft, and the Solar and Heliospheric Observatory (SOHO) spacecraft, we come to the conclusion that the source of the burst is the core of a behind-the-limb CME. We conclude that the radio emission can escape the center of the CME core at a frequency of 60 MHz and originates from the periphery of the core at a frequency of 30 MHz that is due to occultation by the solar corona at the corresponding frequencies. We find plasma densities in these regions assuming the plasma mechanism of radio emission. We show that the frequency drift of the start of the type IV burst is governed by an expansion of the CME core. The type III bursts that were observed against this type IV burst are shown to be generated by fast electrons propagating through the CME core plasma. A type II burst was registered at frequencies of 44 – 64 MHz and 3 – 16 MHz and was radiated by a shock with velocities of about 1000 km s − 1 and 800 km s − 1 , respectively.

Estimating for the frequency drift rates of type III solar bursts is crucial for characterizing their source development in the solar corona. According to Melnik et al. ( Solar Phys. 269 , 335, 2011 ), the analysis of powerful decameter type III solar bursts, observed in July – August 2002, found a linear approximation for the drift rate versus frequency. The conclusion contradicts reliable results of many other well-known solar observations. In this paper we report on the reanalysis of the solar data with a more advanced method. Our study shows that the decameter type III solar bursts of July – August 2002, as standard type III bursts, follow a power law in frequency drift rates. We explain the possible reasons for this discrepancy.

We discuss properties of type III bursts that change the sign of their drift rate from negative to positive and vice versa . Moreover, these bursts may change the sign of their drift rates more than once. These particular type III bursts were observed simultaneously by the radio telescopes UTR-2 ( Ukrainian T-shaped Radio telescope , Kharkov, Ukraine), URAN-2 ( Ukrainian Radio telescope of the Academy of Sciences , Poltava, Ukraine), and by the NDA ( Nançay Decametric Array , Nancay, France) in the frequency range 8 – 41 MHz. The negative drift rates of these bursts are similar to those of previously reported decameter type III bursts and vary from −0.7 MHz s −1 to −1.7 MHz s −1 , but their positive drift rates vary in a wider range from 0.44 MHz s −1 to 6 MHz s −1 . Unlike inverted U-bursts, the tracks of these type III bursts have C- or inverted C-shapes. Our basic explanation of the positive drift rate of these type III bursts differs from the common assumption that positive drift rates of type III bursts are connected with electron beam propagation toward the Sun. We propose that, even if electron beams move outward from the Sun, they can generate type III bursts with positive drift rates if in some regions of the solar corona the group velocities of type III radio emissions are lower than the velocities of the electron beams.