Seasonal effects in the ionosphere-thermosphere response to the precipitation and field-aligned current variations in the cusp region

International audienceThe seasonal effects in the thermosphere and ionosphere responses to the precipitating electron flux and field-aligned current variations, of the order of an hour in duration, in the summer and winter cusp regions have been investigated using the global numerical model of the Earth's upper atmosphere. Two variants of the calculations have been performed both for the IMF By By < 0 but for the Northern (winter) Hemisphere there is a disagreement at high latitudes in the afternoon sector of the cusp region. At the same time, the model results for this sector agree with other DE-2 data and with the ground-based FPI data. All ionospheric and thermospheric disturbances in the second variant of the calculations are more intensive in the winter cusp region in comparison with the summer one and this seasonal difference is larger than in the first variant of the calculations, especially in the electron density and all temperature variations. The means that the seasonal effects in the cusp region are stronger in the thermospheric and ionospheric responses to the FAC variations than to the precipitation disturbances

Models of field-aligned currents needful to simulate the substorm variations of the electric field and other parameters observed by EISCAT

International audienceWe have used the global numerical model of the coupled ionosphere-thermosphere-protonosphere system to simulate the electric-field, ion- and electron-temperature and -concentration variations observed by EISCAT during the substorm event of 25 March 1987. In our previous studies we adopted the model input data for field-aligned currents and precipitating electron fluxes to obtain an agreement between observed and modelled ionospheric variations. Now, we have calculated the field-aligned currents needful to simulate the substrom variations of the electric field and other parameters observed by EISCAT. The calculations of the field-aligned currents have been performed by means of numerical integration of the time-dependent continuity equation for the cold magnetospheric electrons. This equation was added to the system of the modelling equations including the equation for the electric-field potential to be solved jointly. In this case the inputs of the model are the spatial and time variations of the electric-field potential at the polar-cap boundaries and those of the cold magnetospheric electron concentration which have been adopted to obtain the agreement between the observed and modelled ionospheric variations for the substorm event of 25 March 1987. By this means it has been found that during the active phase of the substorm the current wedge is formed. It is connected with the region of the decreased cold magnetospheric electron content travelling westwards with a velocity of about 1 km s?1 at ionospheric levels

РАСЧЕТ ХАРАКТЕРИСТИК ВЫБРОСОВ ВНУТРЕННЕГО ДАВЛЕНИЯ В МАГИСТРАЛЬНЫХ ГАЗОПРОВОДАХ

Management of technological operations during the discharge and filling of gas compressor stations and the linear part of the main gas pipelines, start-ups and shutdowns of gas-pumping units and other technological switches, aimed at avoiding exceeding the limit values ​​of the amplitude of gas oscillations in order to increase the operability of the gas transmission system.&nbsp;Main gas pipelines are designed to ensure safe operation during normal working process.&nbsp; The internal pressure as well as its test pressure are safe and will not cause bursting of the gas pipeline.&nbsp; But often during the operation of the main gas pipeline, there are on-off procedures and various fluctuations.&nbsp; Therefore, due to these processes and cyclic loading, fatigue of the pipeline metal takes place.&nbsp; It is also known from practice that during normal operation, pipeline destruction may occur.&nbsp; Therefore, it is important to determine the value of dynamic pressure emissions, for a high level, which is very important.&nbsp; It was found that the series of internal pressure obeys the Rayleigh distribution law.&nbsp; On the basis of this law, an analytical dependence of the amount of internal pressure emissions for a given level was obtained, according to which numerical results were obtained.Управление технологическими операциями при &nbsp;отведении и заполгнении газом компрессорных станций и линейной части магистральных газопроводов, пусках и остановках газоперекачивающих агрегатов и других технологических переключениях, направленно на исключение превышения предельных значений амплитуды колебаний газа, с целью повышепния работоспособности газотранспортной системы.Магистральные газопроводы спроектированы таким образом, чтобы обеспечить безопасную эксплуатацию при нормальном рабочем процессе. Внутреннее давление, а также его испытательное давление являются безопасными и не вызывают разрыва труб газопровода. Но часто при эксплуатации магистрального газопровода &nbsp;возникают процедуры включения-отключения и разные флуктуации. Поэтому из-за этих процессов и циклического нагружения имеет место усталость металла трубопровода. Также из &nbsp;практикие известно, что при нормальной работе, может происходить разрушение трубопровода. Поэтому, важно определить величину выбросов динамического давления, для высок уровня, что весьма актуально. Установлено, что ряд внутреннего давления подчиняется закону распределения Рэлея. На основе этого закона получена аналитическая зависимость количества выбросов внутреннего давления для данного уровеня, по которой &nbsp;получены численные результаты

PLOTTING A DIAGRAM OF NATURAL GAS INTERCHANGEABILITY FOR THE ENERGY MARKET OF GEORGIA

The increase in the cost of energy and the appearance of gases of various qualities led to the fact that calculations in the gas industry began to be made by measuring thermal energy.&nbsp; To this day, in Georgia, the calculation of the amount of natural gas when paying for the used gas is in cubic meters.&nbsp; As for the study of processes and parameters in the Georgian gas sector, it turned out that these processes are clearly stochastic.&nbsp; Therefore, the purpose of the work is to develop criteria for the interchangeability of natural gas, in particular, a diagram of the interaction between the Wobbe index in total proportions of propane and nitrogen equivalent for the Georgian gas market, based on stochastic processes.&nbsp; Thus, for the first time, an original methodology for plotting the Wobbe Index (calorific value) of interchangeable natural gases supplied to Georgia was developed.The increase in the cost of energy and the appearance of gases of various qualities led to the fact that calculations in the gas industry began to be made by measuring thermal energy.&nbsp; To this day, in Georgia, the calculation of the amount of natural gas when paying for the used gas is in cubic meters.&nbsp; As for the study of processes and parameters in the Georgian gas sector, it turned out that these processes are clearly stochastic.&nbsp; Therefore, the purpose of the work is to develop criteria for the interchangeability of natural gas, in particular, a diagram of the interaction between the Wobbe index in total proportions of propane and nitrogen equivalent for the Georgian gas market, based on stochastic processes.&nbsp; Thus, for the first time, an original methodology for plotting the Wobbe Index (calorific value) of interchangeable natural gases supplied to Georgia was developed

Analysis of the positive ionospheric response to a moderate geomagnetic storm using a global numerical model

International audienceCurrent theories of F-layer storms are discussed using numerical simulations with the Upper Atmosphere Model, a global self-consistent, time dependent numerical model of the thermosphere-ionosphere-plasmasphere-magnetosphere system including electrodynamical coupling effects. A case study of a moderate geomagnetic storm at low solar activity during the northern winter solstice exemplifies the complex storm phenomena. The study focuses on positive ionospheric storm effects in relation to thermospheric disturbances in general and thermospheric composition changes in particular. It investigates the dynamical effects of both neutral meridional winds and electric fields caused by the disturbance dynamo effect. The penetration of short-time electric fields of magnetospheric origin during storm intensification phases is shown for the first time in this model study. Comparisons of the calculated thermospheric composition changes with satellite observations of AE-C and ESRO-4 during storm time show a good agreement. The empirical MSISE90 model, however, is less consistent with the simulations. It does not show the equatorward propagation of the disturbances and predicts that they have a gentler latitudinal gradient. Both theoretical and experimental data reveal that although the ratio of [O]/[N2] at high latitudes decreases significantly during the magnetic storm compared with the quiet time level, at mid to low latitudes it does not increase (at fixed altitudes) above the quiet reference level. Meanwhile, the ionospheric storm is positive there. We conclude that the positive phase of the ionospheric storm is mainly due to uplifting of ionospheric F2-region plasma at mid latitudes and its equatorward movement at low latitudes along geomagnetic field lines caused by large-scale neutral wind circulation and the passage of travelling atmospheric disturbances (TADs). The calculated zonal electric field disturbances also help to create the positive ionospheric disturbances both at middle and low latitudes. Minor contributions arise from the general density enhancement of all constituents during geomagnetic storms, which favours ion production processes above ion losses at fixed height under day-light conditions