Radio Transparency Research Articles

Comparative studies of radio transparency and dielectric characteristics of polymer composites

Aramid-epoxy composites and glass fiber reinforced plastics are widely used in the manufacturing of the fairing design for modern aerospace vehicles due to their excellent mechanical properties combined with radio transparency in wave transfer. In this paper, aramid-epoxy composite and fiberglass were fabricated by the vacuum infusion method for a comparative study on radio transparency and dielectric characteristics. The radio transparency of the studied materials was evaluated by free-space measurements in the frequency range of 1 GHz to 8.5 GHz. According to the radio transparency results, the aramid-epoxy composite undergoes less electromagnetic wave loss than glass fiber reinforced plastic. Modifying the epoxy resin with tricresyl phosphate in aramid-epoxy resin leads to an increase in mechanical properties with a slight decrease in transmittance and a non-significant increase in dielectric characteristics. The dielectric characteristics results have demonstrated low values (ε = 2.87 and tan δ = 0.037) for aramid composites compared to fiberglass.

Comparative study of dielectric characteristics and radio transparency of composite materials

Polymer composites with low dielectric properties and excellent radio transparency are essential for high signal transmission rates and high device integration. However, creating dielectric polymer composites with high radio transparency is a challenging task. This work presents comparative results of studying the dielectric loss, permittivity and radio transparency of composite materials, such as aramid-epoxy composite (AEC), glass fiber (GF), carbon fiber reinforced plastic (CFRP), and ultra-high molecular weight high-density polyethylene (UHMWPE). Based on the experimental results, the following transmission percentages were established for various materials: CFRP – 2.45%, AEC – 79.43%, UHMWPE – 80.16%, and GF – 78.88%. The dielectric loss tangent angle of carbon fiber is significantly higher compared to other polymer composites, UHMWPE exhibits the lowest tangent angle values, and AEC and GF have stable and low dielectric loss. The obtained polymer composites demonstrated low dielectric permittivity values: AEС 2.9, UHMWPE 2.56, and GF 3.64.

SCATTERING OF ELECTROMAGNETIC WAVES ON FLAT GRID TWO-PERIODIC STRUCTURES

Context. One of the scientific hypotheses for the creation of nonreciprocal optical metasurfaces is based on the use of a wave channel in which rays of the direct and reverse diffraction scenarios are realized on two-periodic flat structures with nonlinear elements. Such processes in the nanometer wavelength range of electronic devices require precise calculations of the interaction of waves and microstructures of devices. It is also important to describe the behavior of antenna devices in mobile communications. Expanding the wavelength range of stable communication is achieved by using prefractal structures in antenna devices in combination with periodic structuring. Similar modeling problems arise when electromagnetic waves penetrate materials with a crystalline structure (radio transparency).
 Objective. To test this hypothesis, it is necessary to carry out mathematical modeling of the process of scattering of electromagnetic waves by metasurfaces under conditions of excitation of several diffraction orders. It is known that among two-periodic flat lattices of different structures there are five types that fill the plane. These are the Bravais grilles. The problem of scattering of an incident monochromatic TE polarized wave on a metal screen with recesses in two-periodic structures filled with silicon was considered.
 Method. The paper builds mathematical models for the study of spatial-amplitude spectra of metasurfaces on Brave lattices and gives some results of their numerical study. The condition for determining the diffraction orders propagating over the grating is proposed. Scattered field amplitudes are from the solution of the boundary value problem for the Helmholtz equation in the COMSOL Multiphysics 5.4 package. Similar problem formulations are possible when studying the penetration of an electromagnetic field into a crystalline substance.
 Results. Obtained relations for diffraction orders of electromagnetic waves scattered by a diffraction grating. The existence of wavelengths incident on a two-periodic lattice for which there is no reflected wave is shown for different shapes (rectangular, square, hexagonal) of periodic elements in the center of which a depression filled with silicon was made. Distributions of reflection coefficients for different geometric sizes of colored elements and recesses are given. The characteristics of the electric field at resonant modes in the form of modulus isolines show the nature of the interaction of the field over the periodic lattice and the scatterersdepressions. At the resonant wavelengths of the incident waves, standing waves appear in the scatterers.
 Conclusions. A mathematical model of the set of diffraction orders propagating from a square and hexagonal lattice into halfspace is proposed z >= 0. It has been shown that flat periodic lattice with square or hexagonal periodicity elements and resonant scatterers in the form of cylindrical recesses filled with silicon can produce a non-mirrored scattered field in metal. The response of the lattices to changes in the wavelength of the incident field by the structure of diffraction orders of the scattered field and high sensitivity to the rotation of the incident plane were revealed. The two-periodic lattices have prospects for creating anti-reflective surfaces of various devices. Two-periodic lattices have prospects for creating anti-reflective surfaces for various devices, laser or sensor electronic devices, antennas in mobile communication elements, and radio transparency elements. They have more advanced manufacturing technologies in relation to spatial crystal structures.

STUDY OF RADIO TRANSPARENCY AND DIELECTRIC PERMITTIVITYOF GLASS-AND ARAMID EPOXY COMPOSITES

Aramide-epoxy-filled composites are widely used for manufacturing in the structures of modern aerospace vehicles. Not only do they have excellent mechanical properties, but they are also radio-transparent materials for wave transmission. In this work, an epoxy-filled composite and a fibreglass were made by vacuum infusion for a comparative study on radio transparency and dielectric permittivity. The radio transparency of the materials analyzed has been evaluated by measuring in free space in the frequency ranges of 1-6 GHz. According to the results of radio transparency, aramide-epoxy-filled composite suffers less electromagnetic wave losses than in fibreglass. When measuring the dielectric permittivity of the aramide-epoxy-filled composites, a low average value of 2.874 has been set, whereas for the fibreglass is defined at 4.

PRINCIPLES OF THE CHOICE OF THE COMBINED LIGHTNING PROTECTION FOR COMPOSITE MATERIALS OF DIELECTRIC POLYMERS

General approaches to solving the problem of lightning protection of composite materials are considered. In particular, the use of dielectric composites, which are radio transparent, requires the organization of their reliable lightning protection, which involves the use of conductors. Thus, the development of segment tires creates the prerequisites for realizing the advantages of knitted combined weaves, including metal threads, and requires further research.

DEVELOPMENT OF UNIVERSAL HIGH-STRENGTH MAGNESIUM ALUMINOSILICATE GLASS-CERAMIC MATERIALS FOR ARMOR PROTECTION

The necessity of creating innovative protective structures for armoring machinery and equipment is analyzed. A comparative analysis of high-strength materials used for local and individual body armor has been carried out. The relevance of the development of domestic universal armored materials that combine high strength properties and radio transparency based on lightweight technological magnesium aluminosilicate glass-ceramic materials with high performance properties at the level of world analogues has been determined. Were formulated the purpose and tasks of the work, which consist in: analysis of the current state of development of glass-ceramic materials for armor protection; development of magnesium-aluminosilicate glass-ceramic materials with high armor resistance, impact resistance and radio transparency; investigation of the operational properties of the developed glass-ceramic materials and their armor resistance; assessment of the competitiveness of the developed glass-ceramic materials. A set of requirements for a glass matrix for obtaining protective glass-ceramic materials has been formulated. Compositions and technological parameters for the production of glass-ceramic materials under the conditions of two-stage low-temperature heat treatment have been developed. The study of the electrical properties of experimental glass-ceramic materials made it possible to establish the possibility of effective functioning of on-board wireless communication systems when using the developed materials as elements of armor protection. It was found that the developed glass-ceramic materials are characterized by high operational properties (KCU = 5.8 kJ/m2; HV = 10.4 GPa; K1C = 8.5 MPa∙m1/2) and armor resistance STANAG 4569 (level 2). The competitiveness of the developed glass-ceramic materials based on mullite is analyzed. It has been established that a significant increase in fracture toughness and a decrease in the density of the developed material when comparing properties with a similar armor element (corundum-based plate) will significantly reduce the weight of the armor elements by ≈1.4 times and its cost by five times, while maintaining its protective properties.

Investigation of dielectric and strength properties of organoplastics. Review

Currently, the production and use of military UAVs in the direction of robotic complexes is actively developing. The purpose and use of military UAVs differ from civilian ones, based on two functions: reconnaissance purpose and a carrier of a warhead. The specifics of military UAVs are their invisibility to enemy radars and ensuring stable transmission of information from the command post. For these purposes, first of all, the UAV material must have the properties of radio transparency. For the production of UAV hulls, power elements, high-strength PCM are needed, which include organoplastics, carbon fiber, fiber glass. The choice of materials for parts of components and assemblies of aviation equipment depends on their operating conditions: operating loads, material properties. Organoplastics (OP) fully meets these requirements among polymer composite materials (PCM). OP have high strength properties along with low dielectric losses (radio transparency) compared to other fiber composites. This paper presents an overview of studies of dielectric and strength properties, as well as ways to improve the mechanical properties of organoplastics. The analysis of the work has shown that for radiotransparent organoplasty, the optimal frequency range of permittivity is 1kHz-12 GHz. The ultimate strength of organoplastics varies in the range from 320 MPa to 1 GPa. The possibilities of increasing the strength of aramid fibers and ways of modifying organoplastics epoxy resins are considered.

Radio-γ-ray response in blazars as a signature of adiabatic blob expansion

Context. Multi-wavelength light curves in long-term campaigns show that, for several blazars, the radio emission occurs with a significant delay with respect to the γ-ray band, with timescales ranging from weeks to years. Such observational evidence has long been a matter of debate, and is usually interpreted as a signature of the γ-ray emission originating upstream in the jet, with the emitting region becoming radio transparent at larger scales. Aims. In this paper, we show, by means of self-consistent numerical modelling, that the adiabatic expansion of a relativistic blob can explain these delays, reproducing lags compatible with the observed timescales. Methods. We use the JetSeT framework to reproduce the numerical modelling of the radiative and accelerative processes, reproducing the temporal evolution of a single blob, from the initial flaring activity and the subsequent expansion. We follow the spectral evolution and the corresponding light curves, investigating the relations among the observed parameters, rise time, delay, and decay time, and we identify the link with physical parameters. Results. We find that, when adiabatic expansion is active, lags due to the shift of the synchrotron frequency occur. The corresponding time lags have an offset equal to the distance in time between the flaring onset and the beginning of the expansion, whilst the rising and decaying timescales depend on the velocity of the expansion and on the time required for the source to exhibit a synchrotron self-absorption frequency below the relevant radio spectral window. We derive an inter-band response function, embedding the aforementioned parameters, and we investigate the effects of the competitions between radiative and adiabatic cooling timescales on the response. We apply the response function to long-term radio and γ-ray light curves of Mrk 421, Mrk 501, and 3C 273, finding satisfactory agreement on the log-term behaviour, and we use a Monte Carlo Markov chain approach to estimate some relevant physical parameters. We discuss applications of the presented analysis to polarization measurements and to jet collimation profile kinematics. The collimation profiles observed in radio images are in agreement with the prediction from our model.

Measurement of radio transparency of polycrystalline CVD-diamond in millimeter-wave range by free-space method

Radio transparency of polycrystalline CVD-diamond disks with diameter up to 75 mm in millimeter-wave range was measured by free-space method. The structure of the disks was characterized by Raman spectroscopy and scanning electron microscopy. Dielectric loss tangent of the samples in the frequency range of 50-67 GHz was found to be in the range of 7.5· 10-3-8· 10-2, increasing with frequency. The transmission loss due to the radiation absorption is about 1%. Keywords: millimeter-waves, polycrystalline diamond, radio transparency.

Research of Insertion Loss of Polycrystalline CVD Diamond within Range of 40...80 GHz

Insertion loss of polycrystalline CVD diamond within range of40...80 GHz is investigated by free space method. A diamond disk with diameter 56,6 mm and thickness 366 um was provided by GPI RAS. The disk was found to be radio transparent. Usage of diamond lid to seal LTCC package with T/R MMIC inside resulted in radiation loss by 2,9 dB at 60,5 GHz.

Frequency selective surface with complex topology elements

Relevance: The solution of specific problems in modern technology of microwave and UHF ranges, such as the implementation of reducing the radar signature of objects, spatial frequency-selective filters, reflectors requires the development and creation of a special class of electrodynamic structures - frequency-selective surfaces. Due to the uniqueness of their electrodynamic characteristics, it is possible to solve quite technically complex problems - suppression of excited surface waves, the creation of "forbidden" zones in the amplitude-frequency characteristics. The purpose of the work is numerical modeling and experimental study of electrodynamic characteristics of plane frequency-selective surfaces with slotted elements of complex topology. Evaluation of the influence of the geometric parameters of the slot inhomogeneity and the material constants of the dielectric substrate on the reflection and transmission coefficients of the frequency-selective surface. Materials and methods: The paper presents the results of numerical simulation of the electrodynamic characteristics of a cell of an infinite 2D frequency-selective surface with the topology of a structural element -shaped and experimental studies of the prototype parameters. Modeling was performed within the framework of the finite element method (FEM) using the ANSOFT HFSS / ANSYS software product. Characteristic measurements are performed in free space by direct measurement of attenuation values. Results: In the course of numerical experiments, it was found that two types of resonances can arise in the structure, associated both with the ratio of the geometric dimensions of the structural element and with the presence of double-sided shielding. The influence of the thickness of the dielectric substrate and the values ​​of the dielectric constant on the reflection and transmission coefficients is investigated. The frequency dependences of the reflection value are established with a change in the spatial orientation of the structure relative to the incident wave front. The dependence of the magnitude of the radio transparency of a two-layer frequency-selective surface on the angle of rotation of the structure around a given axis has been established experimentally. Conclusion: The presented results of numerical simulation of the electrodynamic characteristics of a cell of an infinite 2D frequency-selective surface with the topology of a structural element -shaped and experimental studies have shown the possibility of spatial frequency selection. The totality of the results obtained makes it possible to predict the creation of sufficiently technological and highly efficient frequency-selective surfaces in the microwave range.

Исследование потерь пропускания в поликристаллическом CVD-алмазе в миллиметровом диапазоне длин волн методом свободного пространства

Radio transparency of polycrystalline CVD-diamond disks with diameter up to 75 mm in millimeter-wave range was measured by free-space method. The structure of the disks was characterized by Raman spectroscopy and scanning electron microscopy. Dielectric loss tangent tan δ of the samples in the frequency range of 50 – 67 GHz was found to be in the range of 7.5·10−3 − 2.8·10−2, increasing with frequency. The transmission loss due to the radiation absorption is about 1%.

Recurrent Spontaneous Pneumothorax in a Maltese Dog with Endogenous Lipoid Pneumonia

Background: Pneumothorax is a clinical condition which can cause respiratory distress. It can have as its origin traumatic causes or even classified as spontaneous, mainly related to diseases of the lung parenchyma. Lipoid pneumonia is rarely described in dogs, and it is characterized by globules of lipid in the alveolar spaces. Endogenous lipoid pneumonia (EnLP) occurs when lesions on pulmonary cells release cholesterol and other lipids in the alveoli. There is no clinical approach established for EnLP in veterinary patients. The aim of this report is to describe a case of a young Maltese dog, with recurrent spontaneous pneumothorax in which EnLP was diagnosed Post mortem.Case: A 2-year-old sexually intact male Maltese dog was evaluated for restrictive dyspnea. Clinicopathologic findings included cyanotic, muffled chest auscultation with hypersonic thoracic percussion. Chest x-ray demonstrated an increase in pleuropulmonary radio transparency and a floating-looking heart, indicating pneumothorax. Complete blood counts andbiochemical panel results were normal. Dirofilaria immitis antigen test results were negative. Computed tomography demonstrated slightly hyper-expanded pulmonary fields, with slightly enlarged reticular marking with areas of mild multicentric panlobular emphysema and a fracture on the sixth left rib. The treatment was focused on improving the breathing pattern through sedation, supplementation with oxygen, and thoracentesis. Owing to the reserved prognosis of the case, the unknown etiology of the recurrent pneumothorax, and the clinical worsening of the patient, the owner opted for euthanasia. Necropsy displayed multiple, circular whitish areas in the lungs, distributed over the surface of all lobes. Histopathological examination revealed pulmonary tissue with the subpleural micronodular foci, multifocal to coalescent, with a moderate accumulation of foamy intra-alveolar macrophages, occasionally multinucleate, associated with cholesterol crystals compatible with endogenous lipid pneumonia. Discussion: The patient presented with clinical signs and physical examination characteristics of pneumothorax at the first visit. After the pneumothorax diagnosis, and clinical stabilization of the patient. No predisposing factor for the formation of the pneumothorax was identified as the radiography revealed only bronchitis and blood tests were normal, the patient was thus discharged after 24 h, with the recommendations for observing the breathing pattern. Initially, spontaneous pneumothorax was suspected. The antibiotics were administered since bacterial pneumonia, although not confirmed on chest x-ray, is the main cause of pneumothorax in dogs is lung parenchyma disease. With the worsening of the clinical condition of the patient, CT was performed and did not demonstrate any findings that would justify the presence of pneumothorax. Despite the placement of the chest tube for facilitating the management of thoracentesis, there was no stabilization of the condition, enhancing the frequency of centesis procedures, which led to the decision to euthanize. The microscopic examination of the pulmonary alterations was decisive for the diagnostic conclusion. The visualization of the accumulation of foamy intra-alveolar macrophages, occasionally multinucleate, associated with cholesterol crystals, was responsible for the diagnosis of EnLP. This condition is rarely described in dogs and as in the present report, it is a noninfectious inflammatory condition, characterized by intra- or extracellular globules of lipid in the alveolar spaces. In the present report, although it was not possible to determine the etiology of EnLP, we can conclude that although rare, it can affect dogs and can generate severe clinical repercussions.

Creating Conditions for the Industrial Application of Basalt-Plastic Reinforcement in Manufacturing Precast Concrete Structures

The search for alternative methods of replacing steel reinforcement in load-bearing reinforced concrete structures with composite polymer reinforcement is an urgent scientific and practical task. Composite reinforcement (basalt-plastic, fiberglass) is an economically viable alternative to steel reinforcement; it possesses high tensile strength and chemical resistance, light weight (more than 4 times lighter than the steel ones), low thermal conductivity, radio transparency, dielectric properties. Such properties make it possible to use this type of reinforcement of concrete structures in civil, industrial, and road construction. Only in recent years, the specialists in Uzbekistan have paid special attention to the need for composite polymer reinforcement in construction. This type of reinforcement makes it possible to increase the service life of concrete structures and the building as a whole and to reduce the country’s dependence on imports of steel reinforcement. At present the production of basalt-plastic reinforcement is localized in the country – its fiber is made from local basalt. For the possibility of industrial application of composite polymer reinforcement in construction, it is necessary to establish a relationship between a customer, a designer, and a manufacturer. For a customer, the project must be economically profitable, a designer must understand the physical and mechanical properties of the reinforcement and know the regulatory base, and a manufacturer must be interested in producing quality units and assemblies in accordance with the interstate standards, and be sure that the reinforcement produced by him will be in demand. The high deformability of structures caused by the low modulus of elasticity of composite reinforcement does not allow the manufacture of structures that work as bending and eccentrically compressed elements, embedded in reinforced concrete; however, it is noted that such reinforcement can be used in structures for which the requirements for the second group of limiting states are not determinant. The national standards acting in the CIS countries and other states limit the scope of application of composite polymer reinforcement in concrete structures in industrial objects of the economic complex. An analysis of the actual operation of prefabricated road panels, taking into account the low deformation characteristics of basalt-plastic reinforcement, showed the possibility of replacing steel reinforcement with a composite polymer one according to the criterion of uniform strength in terms of design tensile strengths while maintaining the number of working reinforcement bars and their location in reinforcing units.The results of testing the pilot panels of the road surface (prefabricated ones) reinforced with basalt-plastic reinforcement were considered to determine their crack resistance and bearing capacity. The test results of experimental road panels show that the bearing capacity not only decreased but substantially increased. The high corrosion resistance of basalt-plastic reinforcement, when used in road panels, contributes to an increase in the service life of such panels, since the values of crack opening under operational loads are set lower than the permissible limit values. The results of this study show that it is possible to expand the scope of industrial application of basalt-plastic reinforcement in the production of precast concrete structures, for example, for road construction. To do this, it is necessary to create a regulatory framework based on the results of relevant research work.

Dielectric study of syntactic foams based on polydimethylsiloxane and hollow glass microspheres at X-band microwave frequency

The dielectric characteristics of syntactic foams based on polydimethylsiloxane binder and hollow glass microspheres at the X-band microwave frequency were studied. Experimental studies were carried out to determine and calculate dielectric constant, dielectric loss tangent in the range from 8 to 12 GHz, as well as radio transparency of the obtained materials. According to the results, an increase in the binder content over 15-20 vol.% led to a significant loss of radio transparency. The treatment by hydrophobizing organosilicon liquid was shown as an effective method for decreasing the dielectric loss tangent and increasing the radio transparency at the microwave radio frequency range. The developed materials proved the temperature stability and fire resistance. The expected applications of syntactic foams based on the developed materials include the various fields of structural and industrial engineering, in particular, producing the protective constructions for stationary radar stations and radio telescopes.

Gypsum composites with glass granules

The article explored the possibility of reducing the average density of self-reinforced gypsum composites. Gypsum matrix and glass hollow granules leads to the appearance of a synergistic effect. It manifests itself in the formation of a compacted gypsum reinforced matrix, which is filled with microspheres. This provides a modified gypsum stone with high technical indicators. The volume of use of glass hollow granules is increasing every year, including in the construction industry. This material, unique in its properties, provides very high compressive strength, low water absorption, low heat conductivity, high chemical resistance, and radio transparency for its composite materials. The method of obtaining this light filler is a combination of complex physicochemical and hydrodynamic processes that occur during the formation of hollow balls from microparticles of glass melt. Creating effective composites based on glass micro granules as a component in the molding of gypsum products opens up new possibilities for designers and technologists. This will significantly expand their scope.

Диэлектрические характеристики эпоксидной смолы, модифицированной тетраэтоксисиланом, в миллиметровом диапазоне

In this work, the influence of alkoxysilanes introduced into the epoxy resin was studied. That was done in order to study the possibility of using the obtained binders in composite materials with increased radio transparency in the millimetre microwave radio band. Determination of the modified epoxy resin dielectric characteristics in the millimetre microwave radio transparency was carried out by the waveguide method. The measuring complex consisted of a precision measuring line P1-31, a tunable generator on a Gann diode (30-38 GHz), a ferrite gate, and a section of a standard-section waveguide. Based on measurements of the minimum position displacement of the standing wave coefficient by known propagation constants, the free-space wavelength λ0 for a given operating frequency, and the critical wavelength in the waveguide λcr, the loss angle tangent tg(δ) and the permittivity ε were calculated. Calculations of the permittivity ε, the angle of the dielectric loss tg(δ) and the radio transparency loss-ΔР were performed in the MathСad. Moisture absorption of samples was determined by holding them in a desiccator with a humidity of 98 %. The samples were kept in a tightly closed desiccator for 24 hours at a temperature of 25 oC. In addition, the relative moisture absorption was determined using the increase in mass. It was found that the introduction of tetraethoxysilane in the composition in an amount of 1.5-3.5% leads to a decrease in the tangent of the dielectric loss angle. The optimum is observed in the range of the modifier concentration of 2.5-3.5%. This fact confirms that at these concentrations there is a complete interaction of TEOS alkoxygroups with epoxy resin epoxygroups.

Unveiling the engines of fast radio bursts, superluminous supernovae, and gamma-ray bursts

Young, rapidly spinning magnetars are invoked as central engines behind a diverse set of transient astrophysical phenomena, including gamma-ray bursts (GRB), super-luminous supernovae (SLSNe), fast radio bursts (FRB), and binary neutron star (NS) mergers. However, a barrier to direct confirmation of the magnetar hypothesis is the challenge of directly observing non-thermal emission from the central engine at early times (when it is most powerful and thus detectable) due to the dense surrounding ejecta. We present CLOUDY calculations of the time-dependent evolution of the temperature and ionization structure of expanding supernova or merger ejecta due to photo-ionization by a magnetar engine, in order to study the escape of X-rays (absorbed by neutral gas) and radio waves (absorbed by ionized gas), as well as to assess the evolution of the local dispersion measure due to photo-ionization. We find that ionization breakout does not occur if the engine's ionizing luminosity decays rapidly, and that X-rays typically escape the oxygen-rich ejecta of SLSNe only on $\sim 100 \, {\rm yr}$ timescales, consistent with current X-ray non-detections. We apply these results to constrain engine-driven models for the binary NS merger GW170817 and the luminous transient ASASSN-15lh. In terms of radio transparency and dispersion measure constraints, the repeating FRB 121102 is consistent with originating from a young, $\gtrsim 30-100 \, {\rm yr}$, magnetar similar to those inferred to power SLSNe. We further show that its high rotation measure can be produced within the same nebula that is proposed to power the quiescent radio source observed co-located with FRB 121102. Our results strengthen previous work suggesting that at least some FRBs may be produced by young magnetars, and motivate further study of engine powered transients.

Transionospheric radiosounding (Review)

The transionospheric radiosounding (TIS) method has naturally brought together the two most precise methods for scanning and monitoring the ionosphere (ionospheric radiosounding by airborne and ground ionosondes) into a single system. The subsequent development of TIS equipment has led to a qualitative change in the structure and operation of the ionospheric observatory, which greatly broadened the diagnostic capabilities of the ionospheric monitoring and expanded the ionospheric region monitored by the ground station. In fact, it can be said that a closed radiosounding system has been developed. It uses three branches of ionospheric multifrequency ray (or radio wave) fans to monitor the inner and outer ionosphere and to control both of these regions via transillumination of the ionosphere at the boundary of its radio transparency. The advantage of such a system is the full use of the entire range of radiated radio waves, each part of which is responsible for certain components of the diagnostic circuit. The paper presents the results of scientific studies obtained based on TIS data, which have led to the appearance of new and, to some extent, unexpected and previously unknown phenomena and effects. Special attention is paid to the modern stage of development of the TIS concept, which has good prospects for continuous monitoring of the polar ionosphere. It is questioned whether it is expedient to replace the term sounding with the term transillumination. It is noted that TIS was and remains the most precise method of ionosphere diagnostics.

A technique for detection of PeV neutrinos using a phased radio array

The detection of high energy neutrinos (1015–1020 eV) is an important step toward understanding the most energetic cosmic accelerators and would enable tests of fundamental physics at energy scales that cannot easily be achieved on Earth. In this energy range, there are two expected populations of neutrinos: the astrophysical flux observed with IceCube at lower energies (∼1 PeV) and the predicted cosmogenic flux at higher energies (∼1018 eV) . Radio detector arrays such as RICE, ANITA, ARA, and ARIANNA exploit the Askaryan effect and the radio transparency of glacial ice, which together enable enormous volumes of ice to be monitored with sparse instrumentation. We describe here the design for a phased radio array that would lower the energy threshold of radio techniques to the PeV scale, allowing measurement of the astrophysical flux observed with IceCube over an extended energy range. Meaningful energy overlap with optical Cherenkov telescopes could be used for energy calibration. The phased radio array design would also provide more efficient coverage of the large effective volume required to discover cosmogenic neutrinos.