Weak turbulence theory of the non-linear evolution of the ion ring distribution

The nonlinear evolution of an ion ring instability in a low-beta magnetospheric plasma is considered. The evolution of the two-dimensional ring distribution is essentially quasilinear. Ignoring nonlinear processes the time-scale for the quasilinear evolution is the same as for the linear instability 1/t_ql gamma_l. However, when nonlinear processes become important, a new time scale becomes relevant to the wave saturation mechanism. Induced nonlinear scattering of the lower-hybrid waves by plasma electrons is the dominant nonlinearity relevant for plasmas in the inner magnetosphere and typically occurs on the timescale 1/t_ql w(M/m)W/nT, where W is the wave energy density, nT is the thermal energy density of the background plasma, and M/m is the ion to electron mass ratio, which has the consequence that the wave amplitude saturates at a low level, and the timescale for quasilinear relaxation is extended by orders of magnitude

Characterization of the initial filamentation of a relativistic electron beam passing through a plasma

The linear instability that induces a relativistic electron beam passing through a return plasma current to filament transversely is often related to some filamentation mode with wave vector normal to the beam or confused with Weibel modes. We show that these modes may not be relevant in this matter and identify the most unstable mode on the two-stream/filamentation branch as the main trigger for filamentation. This sets both the characteristic transverse and longitudinal filamentation scales in the non-resistive initial stage.Comment: 4 page, 3 figures, to appear in PR

СУЧАСНИЙ СТАН, ДИНАМІКА ЗМІН ТА ПЕРСПЕКТИВИ РОЗВИТКУ ГІДРОТЕХНІЧНИХ МЕЛІОРАЦІЙ У ДНІПРОПЕТРОВСЬКІЙ ОБЛАСТІ

Formulation of the problem. Irrigation is one of the priority areas of agricultural development for Ukraine. According to numerous studies, it has been determined that restoration of irrigated agriculture is a prerequisite for adapting the agricultural sector of the economy to climate change and ensuring Ukraine's food security. Dnipropetrovsk region was among the territories with the largest area of irrigated land. The vast majority of irrigation systems in the region were built in the 70-80's of the last century and operated for about 50 years, and the last reconstruction of the capital reconstruction was carried out more than 30 years ago. About 198.7 thousand hectares of irrigated land are recorded on the territory of the region, of which 163 thnd ha (82% of available capacity) are not used as irrigated. At the same time, operating systems on the area of 35,7 thnd ha (18% of available) are not working at full capacity. Under the condition of reconstruction of the internal irrigation network, it is promising to restore irrigation on an area of 80.4 thnd. ha. Research results. Irrigation of agricultural crops in the Dnipropetrovsk region occurs on the right and left bank of the Dnipro River in 18 administrative districts. An analysis of the dynamics of the change on the right-bank part indicates a trend of reduction of irrigated land by 1.3 times in 2014 as compared to the same indicator in 2004. The irrigated areas of the left-bank part of the Dnipropetrovsk region have a positive tendency to build up. The dynamics of the change in the period of 2004-2014 indicates that the irregular area is slightly but gradually increased 1.36 times.For the purpose of determining the quality of irrigation water and its suitability for irrigation by structural subdivisions subordinated to the regional office of water resources in the Dnipropetrovsk region, 130 samples were sampled at 56 stationary observation points for chemical analysis. Samples of water were selected near the main pumping stations and control basins, in the heads of main channels, from large and small rivers and ponds.The analysis of the results testifies to the threatening tendency of gradual deterioration of the quality of irrigation water. For example, in comparison with the figures for 2004 in relation to 2014, the area of irrigation with water of the 1st class decreased by 2.7 times from 16.85 thnd ha to 6.34 thnd ha. Almost stable trend has the irrigation area, which was watered with 2nd grade water, which increased by 1.35 times and, with the exception of the indicators in 2010, averaging about 12 thnd ha. The most threatening trend is the increase in areas of irrigated water that is not suitable for irrigation without the prior improvement of its physical and chemical parameters. Such territories have grown almost 3 times from 2,2 thnd ha to 6,1 thnd ha. Conclusions. The unsatisfactory technical condition of the conducting network of most canals and drainage systems, violation of irrigation regime and outdated irrigation technique, worsens the reclamation state of a significant part of the irrigated lands of the Dnipropetrovsk region. In this regard, it is necessary to introduce a system of detailed monitoring of land prone to secondary salinity, based on technologies of remote mapping WL-methods. In addition, it is necessary to widely apply methods of field simplified operational control of the technical state of the components of irrigation networks. It is necessary to perform repair and renovation works in a timely manner that will reduce unproductive water losses for filtration from irrigation systems and prevent soil salinization, as well as rational use of water resources. Due to the threatening trend, particular attention should be paid to the quality and quantity of irrigation water. In the absence of control by the authorities on volumes, concentrations and major sources of pollution of surface and groundwater, it is possible that irrigation systems in the future should include technological lines to improve the physical and chemical parameters of irrigation water. The economic feasibility of the issue requires further study.Представлені результати дослідження сучасного стану, динаміки змін та тенденцій розвитку сільськогосподарських гідротехнічних меліорацій на території Дніпропетровській області. Проаналізовано зміну структури поливних площ протягом останніх 50 років. Визначені основні причини зменшення територій зрошення на правобережній та лівобережній частинах області. Показано тенденцію скорочення зрошуваних земель з 198,7 тис. га від наявних потужностей до 29,4 тис. га за сучасних умов експлуатації внаслідок зміни структури аграрного виробництва з кормо-зернової бази для галузі тваринництва до вирощування технічних та зернових культур, а також значного погіршення технічного стану зрошувальних мереж, старіння і зносу технологічних потужностей систем водопостачання і поливної техніки. Представлена зміна зрошуваних площ по районам області у розрізі з 2004 по 2014 рр. та визначені основні фактори їх зменшення або нарощування в залежності від територіального розташування та техніко-економічної доцільності ведення зрошуваного землеробства. Наведені результати досліджень якості поливної води та розподіл зрошуваних площ за її класами. Відмічається загрозлива тенденція до збільшення поливу сільськогосподарських культур водою низької якості або не придатної для зрошення без попереднього поліпшення її фізико-хімічних властивостей. Встановлено, що з 2004 по 2014 рр. площа сільськогосподарських угідь, политих водою 1 класу, зменшилась з 16,85 тис. га до 6,34 тис. га, а водою 3 класу зросла з 2,2 тис. га до 6,1 тис. га. Наведені основні напрямки і шляхи розвитку, а також окреслені перспективи відродження сільськогосподарських гідротехнічних меліорацій на території Дніпропетровської області

Quasilinear Evolution of Kinetic Alfven Wave Turbulence and Perpendicular Ion Heating in the Solar Wind

The measured spectrum of kinetic Alfven wave fluctuations in the turbulent solar wind plasma is used to calculate the electron and ion distribution functions resulting from quasi-linear diffusion. The modified ion distribution function is found to be unstable to long wavelength electromagnetic ion cyclotron waves. These waves pitch angle scatter the parallel ion velocity into perpendicular velocity which effectively increases the perpendicular ion temperature.Comment: 14 pages, 3 figure

An Antenna with a Feeder for a Superconducting Terahertz Josephson Oscillator with Phase Locking

A principal layout of a Josephson terahertz radiation oscillator integrated with a transmitting antenna-lens system and a harmonic mixer (HM) for phase locking of radiation has been proposed and was successfully implemented. Two antenna-feeder systems designed for the central frequencies of 0.3 and 0.6 THz and located on the same chip with the oscillator are numerically simulated and fabricated. A microstrip transmission line between the oscillator and the antenna is used as the feeder. A study was carried out on matching the oscillator power and HM for two designs; the frequency range of pumping HM was 0.25-0.45 and 0.5-0.68 THz for the designs at 0.3 and 0.6 THz, respectively. Good agreement was obtained between experimental results and numerical simulations. A study of the spectral characteristics of the radiation of the oscillator into the external space for the 0.6 THz design using a superconducting integrated spectrometer was carried out. The linewidth of an emission line in free-running regime was of the order of several megahertz; in the phase locking regime down to tens of kilohertz with a signal-to-noise ratio of more than 20 dB was obtained

A superconducting flux-flow oscillator of terahertz range

We have elaborated, fabricated and tested a THz source radiating to open space based on the superconducting flux-flow oscillator (FFO). In this concept, the oscillator is integrated with the transmitting lens antenna based on a slot structure in Nb film with a thickness of ∼200 nm located on the same chip. The slot planar antenna is matched to the oscillator (by input) and to the semielliptical Si lens with a diameter of 10 mm (by output) providing a narrow output beam of THz emission. A harmonic mixer based on the superconductor-insulator-superconductor junction embedded in the "FFO and antenna" integrated structure has been used for the phase locking of the oscillator. Several designs of antenna coupled with the oscillator by microstrip lines have been numerically simulated, and the batches of experimental samples based on Nb-AlN-NbN superconducting trilayers with Rn •A ∼ 20 Ω•μm2 (jc ∼ 10 kA/cm2) have been fabricated and tested. Two different setups were used for experimental study: A THz spectrometer based on the SIS receiver with a high spectral resolution (better than 0.1 MHz) and a Si bolometer. The overall operating range of 250 to 700 GHz is covered by all the developed designs

Morphology of the tropopause layer and lower stratosphere above a tropical cyclone : a case study on cyclone Davina (1999)

During the APE-THESEO mission in the Indian Ocean the Myasishchev Design Bureau stratospheric research aircraft M55 Geophysica performed a flight over and within the inner core region of tropical cyclone Davina. Measurements of total water, water vapour, temperature, aerosol backscattering, ozone and tracers were made and are discussed here in comparison with the averages of those quantities acquired during the campaign time frame. Temperature anomalies in the tropical tropopause layer (TTL), warmer than average in the lower part and colder than average in the upper TTL were observed. Ozone was strongly reduced compared to its average value, and thick cirrus decks were present up to the cold point, sometimes topped by a layer of very dry air. Evidence for meridional transport of trace gases in the stratosphere above the cyclone was observed and perturbed water distribution in the TTL was documented. The paper discuss possible processes of dehydration induced by the cirrus forming above the cyclone, and change in the chemical tracer and water distribution in the lower stratosphere 400–430 K due to meridional transport from the mid-latitudes and link with Davina. Moreover it compares the data prior and after the cyclone passage to discuss its actual impact on the atmospheric chemistry and thermodynamics

ТРЕХЭЛЕКТРОДНЫЙ ВОЗДУШНЫЙ КОММУТАТОР С ГРАФИТОВЫМИ ЭЛЕКТРОДАМИ КВТГ-50 НА НАПРЯЖЕНИЕ ДО ±50 КВ И ИМПУЛЬСНЫЙ ТОК АМПЛИТУДОЙ ДО ±220 КА

Purpose. Development and creation of the simplified construction of a high-voltage heavy-current air three-electrode switchboard with graphite electrodes, intended for operation in composition the powerful generator of large impulsive current of artificial of linear lightning. Methodology. Electrophysics bases of technique of high-voltage and scientific and technical bases of planning of devices of high-voltage impulsive technique. Results. Developed and made a new construction of a high-voltage heavy-current air three-electrode switchboard with the graphite electrodes of KATG-50 on nominal voltage ±50 kV. This construction of switchboard KATG-50 has been passed experimental approbation in composition the heavy-current bit chain of powerful high-voltage generator of the аperiodic impulses of current of artificial linear lightning rationed on operating foreign standards with amplitude of Im=±(200±20) кА at their duration τP=(350±35) μs at level 0,5∙Im. Originality. First in domestic practice of development and creation of high-voltage heavy-current switchboards for the generators of large impulse currents of artificial lightning the ground of necessity of the use for their basic and managing electrodes of electrical engineering graphite is carried out. Practical value. The developed and made high-voltage heavy-current switchboard of cascade-tray KATG-50 from application in its composition of graphite electrodes possesses an enhanceable working resource and enhanceable stability of wearing-out at the use of similar switchboard in the bit chain of powerful pulsed current of the imitated linear lightning.Представлены основные технические характеристики и краткое описание конструкции высоковольтного трехэлектродного сильноточного воздушного коммутатора с графитовыми электродами КВТГ-50 на номинальное напряжение ±50 кВ. Созданный образец коммутатора предназначен для работы в разрядной цепи мощного высоковольтного генератора нормированных микросекундных импульсов тока искусственной молнии с амплитудой Im=±(200±20) кА при их длительности τp=(350±35) мкс на уровне 0,5∙Im. Данный коммутатор каскадного типа из-за применения графитовых электродов обладает повышенным рабочим ресурсом и повышенной стабильностью срабатывания при его использовании в составе генератора тока имитированной линейной молнии.Представлені основні технічні характеристики і короткий опис конструкції високовольтного трьохелектродного сильнострумового повітряного комутатора з графітовими електродами КВТГ-50 на номінальну напругу ±50 кВ. Створений зразок комутатора призначений для роботи в розрядному колі потужного високовольтного генератора нормованих мікросекундних імпульсів струму штучної блискавки з амплітудою Im=±(200±20) кА при їх тривалості τp=(350±35) мкс на рівні 0,5∙Im. Даний комутатор каскадного типу із-за застосування графітових електродів володіє підвищеним робочим ресурсом і підвищеною стабільністю спрацьовування при його використанні у складі генератора струму імітованої лінійної блискавки