Influence of water vapour on the height distribution of positive ions, effective recombination coefficient and ionisation balance in the quiet lower ionosphere

Mesospheric water vapour concentration effects on the ion composition and electron density in the lower ionosphere under quiet geophysical conditions were examined. Water vapour is an important compound in the mesosphere and the lower thermosphere that affects ion composition due to hydrogen radical production and consequently modifies the electron number density. Recent lower-ionosphere investigations have primarily concentrated on the geomagnetic disturbance periods. Meanwhile, studies on the electron density under quiet conditions are quite rare. The goal of this study is to contribute to a better understanding of the ionospheric parameter responses to water vapour variability in the quiet lower ionosphere. By applying a numerical D region ion chemistry model, we evaluated efficiencies for the channels forming hydrated cluster ions from the NO⁺ and O₂⁺ primary ions (i.e. NO⁺.H₂O and O₂⁺.H₂O, respectively), and the channel forming H⁺(H₂O)_<i>n</i> proton hydrates from water clusters at different altitudes using profiles with low and high water vapour concentrations. Profiles for positive ions, effective recombination coefficients and electrons were modelled for three particular cases using electron density measurements obtained during rocket campaigns. It was found that the water vapour concentration variations in the mesosphere affect the position of both the Cl₂⁺ proton hydrate layer upper border, comprising the NO⁺(H₂O)_<i>n</i> and O₂⁺(H₂O)_<i>n</i> hydrated cluster ions, and the Cl₁⁺ hydrate cluster layer lower border, comprising the H⁺(H₂O)_<i>n</i> pure proton hydrates, as well as the numerical cluster densities. The water variations caused large changes in the effective recombination coefficient and electron density between altitudes of 75 and 87 km. However, the effective recombination coefficient, &alpha;_eff, and electron number density did not respond even to large water vapour concentration variations occurring at other altitudes in the mesosphere. We determined the water vapour concentration upper limit at altitudes between 75 and 87 km, beyond which the water vapour concentration ceases to influence the numerical densities of Cl₂⁺ and Cl₁⁺, the effective recombination coefficient and the electron number density in the summer ionosphere. This water vapour concentration limit corresponds to values found in the H₂O-1 profile that was observed in the summer mesosphere by the Upper Atmosphere Research Satellite (UARS). The electron density modelled using the H₂O-1 profile agreed well with the electron density measured in the summer ionosphere when the measured profiles did not have sharp gradients. For sharp gradients in electron and positive ion number densities, a water profile that can reproduce the characteristic behaviour of the ionospheric parameters should have an inhomogeneous height distribution of water vapour

Quantitative relation between PMSE and ice mass density

Radar reflectivities associated with Polar Mesosphere Summer Echoes (PMSE) are compared with measurements of ice mass density in the mesopause region. The 54.5 MHz radar Moveable Atmospheric Radar for Antarctica (MARA), located at the Wasa/Aboa station in Antarctica (73° S, 13° W) provided PMSE measurements in December 2007 and January 2008. Ice mass density was measured by the Solar Occultation for Ice Experiment (SOFIE). The radar operated continuously during this period but only measurements close to local midnight are used for comparison, to coincide with the local time of the measurements of ice mass density. The radar location is at high geographic latitude but low geomagnetic latitude (61°) and the measurements were made during a period of very low solar activity. As a result, background electron densities can be modelled based on solar illumination alone. We find a close correlation between the time and height variations of radar reflectivity and ice mass density, at all PMSE heights, from 80 km up to 95 km. A quantitative expression relating radar reflectivities to ice mass density is found, including an empirical dependence on background electron density. Using this relation, we can use PMSE reflectivities as a proxy for ice mass density, and estimate the daily variation of ice mass density from the daily variation of PMSE reflectivities. According to this proxy, ice mass density is maximum around 05:00–07:00 LT, with lower values around local noon, in the afternoon and in the evening. This is consistent with the small number of previously published measurements and model predictions of the daily variation of noctilucent (mesospheric) clouds and in contrast to the daily variation of PMSE, which has a broad daytime maximum, extending from 05:00 LT to 15:00 LT, and an evening-midnight minimum

The dynamical background of polar mesosphere winter echoes from simultaneous EISCAT and ESRAD observations

On 30 October 2004 during a strong solar proton event, layers of enhanced backscatter from altitudes between 55 and 75km have been observed by both ESRAD (52MHz) and the EISCAT VHF (224MHz) radars. These echoes have earlier been termed Polar Mesosphere Winter Echoes, PMWE. After considering the morphology of the layers and their relation to observed atmospheric waves, we conclude that the radars have likely seen the same phenomenon even though the radars&apos; scattering volumes are located about 220km apart and that the most long-lasting layer is likely associated with wind-shear in an inertio-gravity wave. An ion-chemistry model is used to determine parameters necessary to relate wind-shear induced turbulent energy dissipation rates to radar backscatter. The model is verified by comparison with electron density profiles measured by the EISCAT VHF radar. Observed radar signal strengths are found to be 2-3 orders of magnitude stronger than the maximum which can be expected from neutral turbulence alone, assuming that previously published results relating radar signal scatter to turbulence parameters, and turbulence parameters to wind shear, are correct. The possibility remains that some additional or alternative mechanism may be involved in producing PMWE, such as layers of charged dust/smoke particles or large cluster ions

Polar mesosphere winter echoes during solar proton events

Thin layers of enhanced radar echoes in the winter mesosphere have been observed by the ESRAD 52 MHz MST radar (67°53 \u27 N, 21°06 \u27 E) during several recent solar proton events. These polar mesosphere winter echoes (PMWE) can occur at any time of day or night above 70 km altitude, whereas below this height they are seen only during daytime. An energy deposition / ion-chemical model is used to calculate electron and ion densities from the observed proton fluxes. It is found that PMWE occurrence correlates well with low values of λ(the ratio of negative ion density to electron density). There is a sharp cut-off in PMWE occurrence at λ～10^, which is independent of electron density. No direct dependence of PMWE occurrence on electron density can be found within the range represented by the solar proton events, with PMWE being observed at all levels of electron density corresponding to values of λ. Together with results concerning the thickness, echo aspect-sensitivity and echo spectral-width of the PMWE, this observation leads to the conclusion that the layers cannot be explained by turbulence alone. A role for charged aerosols in creating PMWE is proposed

Cosmic radio-noise absorption bursts caused by solar wind shocks

Bursts of cosmic noise absorption observed at times of sudden commencements (SC) of geomagnetic storms are examined. About 300SC events in absorption for the period 1967-1990 have been considered. It is found that the response of cosmic radio-noise absorption to the passage of an interplanetary shock depends on the level of the planetary magnetic activity preceding the SC event and on the magnitude of the magnetic field perturbation associated with the SC (as measured in the equatorial magnetosphere). It is shown that for SC events observed against a quiet background (Kp&lt;2), the effects of the SC on absorption can be seen only if the magnitude of the geomagnetic field perturbation caused by the solar wind shock exceeds a threshold value &Delta;Bth. It is further demonstrated that the existence of this threshold value, &Delta;Bth, deduced from experimental data, can be related to the existence of a threshold for exciting and maintaining the whistler cyclotron instability, as predicted by quasi-linear theory. SC events observed against an active background (Kp&lt;2) are accompanied by absorption bursts for all magnetic field perturbations, however small. A quantitative description of absorption bursts associated with SC events is provided by the whistler cyclotron instability theory

Міжнародна електронна торгівля як фактор розвитку економіки на сучасному етапі

Осепян, Г. Г. Міжнародна електронна торгівля як фактор розвитку економіки на сучасному етапі = International e-commerce as a factor in economic development at the present stage : бакалаврська робота ; спец. 051 "Економіка" / Г. Г. Осепян ; наук. кер. Л. Ю. Вдовиченко. – Миколаїв : НУК, 2022. – 58 с.Осепян Г. Г. Міжнародна електронна торгівля як фактор розвитку економіки на сучасному етапі – бакалаврська робота на здобуття ступеня вищої освіти «бакалавр». – Національний університет кораблебудування імені адмірала Макарова, м. Миколаїв, 2022. У роботі висвітлено передумови та рушійні сили розвитку електронної торгівлі на сучасному етапі переходу до цифрової економіки, розглянуто роль, переваги та проблеми функціонування електронної комерції у міжнародній торгівлі. Доведено, що подальший розвиток правового регулювання електронної торгівлі в спеціальних законах України – це питання, які потребують вирішення, а саме: гармонізація системи регулювання електронної комерції України з ЄС, що сприяє зростанню економіки та надасть можливість Україні в майбутньому інтегруватися до Єдиного цифрового ринку. У роботі проаналізовано стан розвитку електронної торгівлі за кордоном та в Україні, досліджено основні тенденції, що сформувались у даній сфері, на підставі чого зазначено напрями та перспективи розвитку міжнародної електронної торгівлі, а також запропоновано механізм державного регулювання ринку електронної комерції в Україні на основі застосування технології «хмарне програмування».Osepian H. G. International e-commerce as a factor in economic development at the present stage – a bachelor’s degree to obtain a degree of «bachelor». – Admiral Makarov National University of Shipbuilding, Mykolayiv, 2022. The preconditions and driving forces of e-commerce development at the present stage of transition to digital economy are covered, the role, advantages and problems of e-commerce functioning in international trade are considered. It is proved that further development of legal regulation of e-commerce in special laws of Ukraine is an issue that needs to be addressed, namely: harmonization of e-commerce regulation of Ukraine with the EU, which promotes economic growth and enables Ukraine to integrate into the Digital Single Market. The state of e-commerce development abroad and in Ukraine is analyzed, the main tendencies formed in this sphere are investigated, on the basis of which directions and prospects of international e-commerce development are indicated, and the mechanism of state regulation of e-commerce market in Ukraine based on technology is offered «Cloud programming»