First imaging spectroscopy observations of solar drift pair bursts

Drift pairs are an unusual and puzzling type of fine structure sometimes observed in dynamic spectra of solar radio emission. They appear as two identical short narrowband drifting stripes separated in time; both positive and negative frequency drifts are observed. Currently, due to the lack of imaging observations, there is no satisfactory explanation for this phenomenon. Using the Low Frequency Array (LOFAR), we report unique observations of a cluster of drift pair bursts in the frequency range of 30−70 MHz made on 12 July 2017. Spectral imaging capabilities of the instrument have allowed us for the first time to resolve the temporal and frequency evolution of the source locations and sizes at a fixed frequency and along the drifting pair components. Sources of two components of a drift pair have been imaged and found to propagate in the same direction along nearly the same trajectories. Motion of the second component source is seen to be delayed in time with respect to that of the first one. The source trajectories can be complicated and non-radial; positive and negative frequency drifts correspond to opposite propagation directions. The drift pair bursts with positive and negative frequency drifts, as well as the associated broadband type-III-like bursts, are produced in the same regions. The visible source velocities are variable from zero to a few 104 (up to ∼105) km s−1, which often exceeds the velocities inferred from the drift rate (∼104 km s−1). The visible source sizes are of about 10′−18′; they are more compact than typical type III sources at the same frequencies. The existing models of drift pair bursts cannot adequately explain the observed features. We discuss the key issues that need to be addressed, and in particular the anisotropic scattering of the radio waves. The broadband bursts observed simultaneously with the drift pairs differ in some aspects from common type III bursts and may represent a separate type of emission

An Introduction to Hyperbolic Barycentric Coordinates and their Applications

Barycentric coordinates are commonly used in Euclidean geometry. The adaptation of barycentric coordinates for use in hyperbolic geometry gives rise to hyperbolic barycentric coordinates, known as gyrobarycentric coordinates. The aim of this article is to present the road from Einstein's velocity addition law of relativistically admissible velocities to hyperbolic barycentric coordinates along with applications.Comment: 66 pages, 3 figure

Turbulent kinetic energy in the energy balance of a solar flare

The energy released in solar flares derives from a reconfiguration of magnetic fields to a lower energy state, and is manifested in several forms, including bulk kinetic energy of the coronal mass ejection, acceleration of electrons and ions, and enhanced thermal energy that is ultimately radiated away across the electromagnetic spectrum from optical to X-rays. Using an unprecedented set of coordinated observations, from a suite of instruments, we here report on a hitherto largely overlooked energy component -- the kinetic energy associated with small-scale turbulent mass motions. We show that the spatial location of, and timing of the peak in, turbulent kinetic energy together provide persuasive evidence that turbulent energy may play a key role in the transfer of energy in solar flares. Although the kinetic energy of turbulent motions accounts, at any given time, for only \sim (0.5-1)\% of the energy released, its relatively rapid (\sim1-10~s) energization and dissipation causes the associated throughput of energy (i.e., power) to rival that of major components of the released energy in solar flares, and thus presumably in other astrophysical acceleration sites

Impact of Friction Stir Processing Parameters on Forming the Structure and Properties in AISI 420 Steel Surface Layer

Research has been done into the influence of friction thermomechanical treatment parameters on forming the structure and properties in a surface layer of 20X13 steel. The paper presents a theoretical approach towards controlling the process variables. A hardened layer with a thickness of 1,7 mm was obtained after 20X13 steel had been subjected to the process. The thickness of the layer that had a microhardness of ≥600HV0,05 turned out to be about 0,75mm while the microstructure of the hardened layer was martensitic, martensitic and perlitic with dispersed inclusions of carbides. It was established that the feed has the biggest influence on the thickness of the hardened layer.     Keywords: friction stir processing, rotation speed, tool feed, normal force, microhardness, microstructure

Copper Recovery from Water of Soryinskoye Tailing Pond

The large volume of recycling waters from the Soryinskoye tailing pond (up to 1300 m3/h) offers interesting possibilities for processing concentrates despite the low copper content (5.2-16.4 mg/l). Sulfides precipitation is the most efficient method of heavy metal ions removal from water. In this study, a sulfur solution in sodium hydroxide was used as a sulfidizing agent for precipitation. Commercial liquid alkali (NaOH – 46) and commercial sulfur were the initial agents. Due to the concentrated alkali, dissolution could be carried out at 115-120∘С, which is higher than the melting point of sulfur. Stable solutions were obtained at a weight ratio of NaOH: S = 1: 1 and a sulfur concentration of 350 g/l. During the laboratory and scale-up laboratory tests, the optimal consumption of sulfidizing agent was determined (110% of the stoichiometry for the formation of Cu2S, and copper extraction into the precipitate from the solution was more than 90.0% with high selectivity towards Zn and Fe). An extended analysis of the composition of the sediment (x-ray fluorescence spectrometer SPECTRO XEPOS) obtained during pilot trials showed that the main elements are, %: sulfur 58.4; oxygen 16.2; copper 8.9; iron 5.7; calcium 4.7 and arsenic 3.8. The total fraction of impurity elements does not exceed 2.3%. This study assumes use of the product conditioning to obtain concentrate with increased copper content and sulfur return to sulfidation stage. Keywords: acid mine drainage, copper recovery, chemical treatment, sulfide precipitatio

First Record of Mites of the Family Stigmaeidae (Acari, Raphignathoidea) from Rovno Amber with Description of a New Species of the Genus Mediolata

A new species, Mediolata eocenica Kuznetsov, Khaustov et Perkovsky, sp. n., is described from the Late Eocene Rovno amber. It is the first fossil record of Stigmaeidae.Описан новый вид клещей Mediolata eocenica Kuznetsov, Khaustov et Perkovsky, sp. n. из позднеэоценового ровенского янтаря. Клещи семейства Stigmaeidae впервые обнаружены в ископаемом состоянии

Structural Properties of the SnxSy Films Obtained by the Thermal Vacuum Co-evaporation

The present work deals with the study of the structural properties of the SnxSy thin films deposited by the closed-spaced vacuum co-evaporation (CSVCE) method. Calculation of temperature dependencies of the sulfur and tin vapor pressures allows to estimate growth conditions of the films with the stoichiometric composition. The effect of growth conditions on surface morphology and structural properties of SnxSy films were studied. Surface morphology of obtained films was determined by the scanning electron microscope (SEM-102Е). Structural investigations of the films were performed with the X-ray diffraction (XRD) method. The analysis of chemical composition of the layers was carried out by the scanning electron microscope by energy dispersive X-ray (ЕDAX) spectroscopy. Influence of the substrate temperature on chemical composition of thin films and their structural characteristics was also investigated