Turbulent spectra and spectral kinks in the transition range from MHD to kinetic Alfv\'en turbulence

A weakly dispersive sub-range (WDR) of kinetic Alfv\'en turbulence is distinguished and investigated for the first time in the context of MHD/kinetic turbulence transition. We found perpendicular wavenumber spectra ~ k^{-3} and ~ k^{-4} formed in WDR by strong and weak turbulence of kinetic Alfv\'en waves (KAWs), respectively. These steep WDR spectra connect shallower spectra in the MHD and strongly dispersive KAW sub-ranges, which results in a specific double-kink (2-k) pattern often seen in observed turbulent spectra. The first kink occurs where MHD turbulence transforms into weakly dispersive KAW turbulence; the second one is between weakly and strongly dispersive KAW sub-ranges. Our analysis suggests that the partial turbulence dissipation due to amplitude-dependent super-adiabatic ion heating may occur in the vicinity of the first spectral kink. A threshold-like nature of this process results in a conditional selective dissipation affecting only largest over-threshold amplitudes and decreasing intermittency in the range below the first spectral kink. Several recent counter-intuitive observational findings can be explained by the selective dissipation coupled to the nonlinear interaction among weakly dispersive KAWs.Comment: 11 pages, 3 figure

Modification of Proton Velocity Distributions by Alfvenic Turbulence in the Solar Wind

In the present paper, the proton velocity distribution function (VDF)in the solar wind is determined by solving numerically the kinetic evolution equation. We compare the results obtained when considering the effects of ex- ternal forces and Coulomb collisions with those obtained by adding effects of Alfven wave turbulence. We use Fokker-Planck diffusion terms due to Alfvenic turbulence, which take into account observed turbulence spectra and kinetic effects of finite proton gyroradius. Assuming a displaced Maxwellian for the proton VDF at the simulation boundary at 14 solar radii, we show that the turbulence leads to a fast (within several solar radii) development of the anti-sunward tail in the proton VDF. Our results provide a natural explanation for the nonthermal tails in the proton VDFs, which are often observed in-situ in the solar wind beyond 0.3 AU

Integrated Assessment of Irrigation Water Quality Based on Harrington\u27s Desirability Function

It was proposed the integrated approach to the irrigation water assessment as its quality index IWQI. This criteria is united the quantitative assessment of different risks such as soil sodicity, plant toxicity, biofilm formation in drippers of irrigation systems etc. It is proposed to combine agronomic, ecological and technological requirements to the irrigation water using a generalized Harrington\u27s desirability function (HDF). Within the framework of this concept, it was developed the scales of particular HDF for physico-chemical indicators, SAR values, and the Stebler\u27s irrigation coefficient. IWQI was determined for the assessment of water quality for irrigation purpose on the examples of 3 dug wells located on the Agronomic Experimental station of National University of Life and Environmental Sciences of Ukraine (Pshenichne village, Kiev region). It is shown that water quality varies considerably (from 56 till 85%)

Non-resonant Alfv\'enic instability activated by high temperature of ion beams in compensated-current astrophysical plasmas

Context: Compensated-current systems are established in response to hot ion beams in terrestrial foreshock regions, around supernova remnants, and in other space and astrophysical plasmas. Aims: We study a non-resonant reactive instability of Alfv\'en waves (AWs) propagating quasi-parallel to the background magnetic field $\mathbf{B}_{0}$ in such systems. Methods: The instability is investigated analytically in the framework of kinetic theory applied to the hydrogen plasmas penetrated by hot proton beams. Results: The instability arises at parallel wavenumbers $k_{z}$ that are sufficiently large to demagnetize the beam ions, $k_{z}V_{Tb}/\omega_{Bi}\gtrsim$ $1$ (here $V_{Tb}$ is the beam thermal speed along $\mathbf{B}_{0}$ and $\omega _{Bi}$ is the ion-cyclotron frequency). The Alfv\'en mode is then made unstable by the imbalance of perturbed currents carried by the magnetized background electrons and partially demagnetized beam ions. The destabilizing effects of the beam temperature and the temperature dependence of the instability threshold and growth rate are demonstrated for the first time. The beam temperature, density, and bulk speed are all destabilizing and can be combined in a single destabilizing factor $\alpha_{b}$ triggering the instability at {$\alpha _{b}>$ $\alpha _{b}^{\mathrm{thr}}$}, where the threshold varies in a narrow range $2.43\leq$ $\alpha _{b}^{\mathrm{thr}}\leq$ $4.87$. New analytical expressions for the instability growth rate and its boundary in the parameter space are obtained and can be directly compared with observations. Two applications to terrestrial foreshocks and foreshocks around supernova remnants are shortly discussed. In particular, our results suggest that the ions reflected by the shocks around supernova remnants can drive stronger instability than the cosmic rays

Peculiarities of britlle and ductile materials destruction and deformation during the explosion of industrial shaped charges

Purpose. To study the laws of deformation and destruction of brittle and ductile rocks and concretes under explosion of industrial shaped charges. Methods. In experiments, the following methods of investigation were used: method of contact sensors for determination of jet velocity; determination of the ultrasonic wave velocity in the concrete samples; methods of optical and electronic microscopy; X-ray phase analysis; measuring and visual analysis of the dimensions and nature of deformation and destruction zones. Findings. The work describes the experimental data on the destruction of barriers made of concrete, granite, steel ST 3, AMC-n alloy, and zinc by the explosions of shaped charges of serial production with porous liners. Calculation formulas for estimating the radius of a destruction zone of geomaterials and rocks in case of a semi-infinite barrier are suggested. The calculation method is based on the estimation of energy impact on the rock by jet penetration velocity into the barrier. Jet velocities are determined experimentally and by engineering methods. The reasons for deviations in the hole shape and deflection of the destruction zone from the symmetry axis were determined. Originality. The modes of penetration of shaped jets into rocks of different porosity, the size of the fracture zone around the hole and the causes and mechanisms of the deviations of the hole shape from the symmetric one are established. Practical implications. The results of the research will be used to design blasting-and-perforation operations in geotechnological wells and can be used to design initiating devices for borehole charges.Мета. Дослідження закономірностей деформування й руйнування крихких і пластичних гірських порід та бетонів при вибуху промислових кумулятивних зарядів. Методика. Метод контактних датчиків для визначення швидкості струменя; визначення швидкості ультразвукових хвиль у зразках бетону; оптична та електронна мікроскопія; рентгенофазний аналіз; вимірювання й візуальний аналіз розмірів та характеру зон деформування і руйнування. Результати. В роботі описані експериментальні дані про деформацію та руйнування перешкод з бетону, граніту, пінобетону, сталі Ст 3, сплаву АМЦ-н і цинку вибухами кумулятивних зарядів серійного виробництва з пористим облицюванням. Запропоновано розрахункові формули для оцінки радіусу зони руйнування геоматеріалів і гірських порід у разі напівнескінченної перешкоди. Визначено причини відхилень форми отвору і зони руйнування від осі симетрії. Наукова новизна. Визначено режими проникнення кумулятивних струменів у породи різної пористості, розміри зони руйнування навколо отвору, а також причини і механізми відхилення форми отвору від симетричної. Практична значимість. Результати досліджень будуть використані для проектування вибухо-прострілочних робіт у геотехнологічних свердловинах і можуть бути використані для конструювання ініціюючих пристроїв свердловинних зарядів.Цель. Исследование закономерностей деформирования и разрушения хрупких и пластичных горных пород и бетонов при взрыве промышленных кумулятивных зарядов. Методика. Метод контактных датчиков для определения скорости струи; определение скорости ультразвуковых волн в образцах бетона; оптическая и электронная микроскопия; рентгенофазный анализ; измерение и визуальный анализ размеров и характера зон деформирования и разрушения. Результаты. В работе описаны экспериментальные данные о деформировании и разрушении преград из бетона, гранита, пенобетона, стали Ст 3, сплава АМЦ-н и цинка взрывами кумулятивных зарядов серийного производства с пористыми облицовками. Предложены расчетные формулы для оценки радиуса зоны разрушения геоматериалов и горных пород в случае полубесконечной преграды. Определены причины отклонений формы отверстия и зоны разрушения от оси симметрии. Научная новизна. Определены режимы проникания кумулятивных струй в породы различной пористости, размеры зоны разрушения вокруг отверстия, а также причины и механизмы отклонения формы отверстия от симметричной. Практическая значимость. Результаты исследований будут использованы для проектирования взрыво-прострелочных работ в геотехнологических скважинах и могут быть использованы для конструирования инициирующих устройств скважинных зарядов.The authors extend their sincere gratitude to the staff of Scientific Research Centre “Materialoobrobka vybukhom” (Processing Materials by Explosion) of the Paton Institute of Electric Welding affiliated with the National Academy of Sciences of Ukraine for the assistance in organization and conducting of the research. We would like to express special thanks to S.I. Kochetkov for the provided data on the velocity of longitudinal sound in solid sandy rocks, and to V.P. Bugaits for the assistance in experiments

Farley-Buneman Instability in the Solar Chromosphere

The Farley-Buneman instability is studied in the partially ionized plasma of the solar chromosphere taking into account the finite magnetization of the ions and Coulomb collisions. We obtain the threshold value for the relative velocity between ions and electrons necessary for the instability to develop. It is shown that Coulomb collisions play a destabilizing role in the sense that they enable the instability even in the regions where the ion magnetization is greater than unity. By applying these results to chromospheric conditions, we show that the Farley-Buneman instability can not be responsible for the quasi-steady heating of the solar chromosphere. However, in the presence of strong cross-field currents it can produce small-scale, $\sim 0.1-3$ m, density irregularities in the solar chromosphere. These irregularities can cause scintillations of radio waves with similar wave lengths and provide a tool for remote chromospheric sensing