10 research outputs found
Directional features of the downshifted peak observed in HF-induced stimulated electromagnetic emission spectra obtained using an interferometer
No full textInternational audienceA high frequency (HF) ionospheric modification experiment was carried out between 25 September and 8 October 2004, using the EISCAT HF transmitter located near Tromsø, Norway. During this experiment the spectra of the stimulated HF sideband waves (stimulated electromagnetic emission or SEE) induced by the HF pump were observed using an interferometer consisting of three spaced receiving antennas with baselines both along and perpendicular to the meridian, and a multi-channel coherent receiver, installed in the vicinity of the HF facility. The transmitter operated at 4040kHz and its antenna beam was scanned to angles of 0°, 7°, 14°, and 21° south from vertical, pausing 4min at each position. This paper focuses on features of the downshifted peak (DP) emission, which has not been as thoroughly studied as many of the other SEE spectral features observable within the EISCAT pump frequency range. It was found that the signal-weighted direction of the DP source region remained within 5° of magnetic zenith as the HF beam was tilted between 0 and 21° south of vertical
Physics of Auroral Phenomena
No full textAbstract Mathematical modelling has been performed to study positive ionospheric storm dependence on the initial state of the plasmasphere. The self-consistent global model of the Earth's upper atmosphere was used. The calculation was made for the case of the geomagnetic storm of August 15, 1993. The locations of auroral precipitation and fieldaligned current regions were set in agreement with the DMSP satellites data. Energy and intensity of precipitating electron fluxes were taken as functions of geomagnetic activity. A numerical experiment demonstrated that storminduced neutral wind effect in ionospheric F2 region electron density is strongly dependent on the initial plasmasphere state, namely, on the degree of plasmaspheric tube filling
Spatial–temporal trends of Late Mesozoic plume magmatism in the Arctic during formation of the Amerasian Basin
No full textManifestation of Small-Scale Artificial Ionospheric Irregularities in Electron Density Measurements by the Methods of Incoherent Scattering and Radio Sounding
No full textAn interferometer experiment to explore the aspect angle dependence of stimulated electromagnetic emission spectra
No full textInternational audienceWhen the Earth's ionosphere is irradiated by a radiofrequency (RF) electromagnetic wave of sufficiently high power density and tuned to match a natural E- or F-region plasma frequency, ionospheric magnetoionic wave modes may be excited and may generate RF electromagnetic sideband waves via nonlinear interactions. These secondary emissions, which may then escape from the ionosphere, have been termed stimulated electromagnetic emission or SEE. The frequency spectra of this radiation has been studied extensively, and a number of characteristic spectral features have been identified and in some cases related to particular plasma processes. The separation in frequency between the RF pump and the harmonics of the local electron gyrofrequency is critical in determining the amount of anomalous absorption suffered by the pump wave and the spectral properties of the stimulated sidebands. The pump can excite electrostatic waves which do not propagate away but can in some cases be observed via radio-wave scattering from the electron density fluctuations associated with them. These enhanced density fluctuations are created by processes commonly referred to as upper-hybrid and Langmuir turbulence. Langmuir turbulence has been the subject of 930-MHz scattering observations with antenna scanning through several pre-selected angles between the geographic and geomagnetic zenith directions, and a preference for pointing angles between the Spitze angle and geomagnetic field-aligned was identified. Other phenomena, such as the generation of enhanced electron temperatures and artificial aurora, have more recently been shown to have special behavior at similar angles, near but apparently not quite at field-aligned. In view of this evidence for angular structure in several pump-induced effects, in light of the rich variety of SEE phenomena strongly dependent on the geomagnetic field via the frequency interval between the pump and the gyrofrequency harmonics, and in view of the not yet understood but complex relationship between electrostatic fluctuations and SEE, it is of interest to investigate experimentally whether a similar angular structure is present in the various spectral features of the SEE signals and to compare the results with radar and other observations of RF-pump-induced effects. To this end we describe a simple two-element radio interferometer designed to search for aspect angle dependence of SEE features. We present an example of the initial data produced by this system, and draw preliminary conclusions based on the example data
Total Electron Content Measurements in the Ionosphere Disturbed by High-Power High-Frequency Waves by the Methods of Incoherent Scattering of Radio Waves and Radio Sounding by Glonass Satellite Signal
No full textWe present the results of comparing the total electron content measurements based on GLONASS
satellite signals and the EISCAT UHF incoherent scatter radar (Tromsø, Norway) during modification of the high-latitude ionosphere in the magnetic zenith direction by high-frequency radio
waves of the EISCAT/Heating facility (Tromsø, Norway). The measurements were performed
during two experiment campaigns in October 2013 and in October 2018. In general, the total electron content variations obtained from the radar data in the altitude range 100–400 km
were consistent with the total electron content variations from the GLONASS satellites. The
efficiency of using GLONASS satellites for observations of high-latitude phenomena was shown.
The anomalous increase in the total electron content by 4 TECU obtained from the incoherent
scatter radar when the ionosphere was heated in the region close to the magnetic zenith is considered. The GLONASS satellite data show the total electron content reduction in the same region.
To explain the disagreement between measurements by these two methods, the effect of smallscale electron-density irregularities arising in the region modified by high-power HF radio waves
is considered. It is shown that when the electron density in artificial irregularities exceeds the
background density of the medium by 2 · 10−3 times in relative units, scattering by irregularities
with spatial scales of the order of 16 cm becomes predominant in the reflected signal
On Spatial Structuring of the F2 Layer Studied by the Satellite Radio Sounding of the Ionosphere Disturbed by High-Power HF Radio Waves
No full textImproving the use of manufacturing funds how to supply sources of competitiveness of domestic enterprises
No full textCrowdsourced estimation of cognitive decline and resilience in Alzheimer's disease
No full textpeer reviewe
Enterprise management in crisis situations: modern approaches, methods, anti-crisis strategies
No full textВ умовах війни та економічної нестабільності надзвичайно важливим у діяльності будь-
якого підприємства є реагування на виникнення кризових ситуацій, що можуть призвести до розвитку
кризового стану та навіть криз. Тому сучасним керівникам і менеджерам необхідно своєчасно виявляти
можливі джерела кризових явищ, застосовувати ефективні інструменти щодо їх подолання, а також
упроваджувати в свою діяльність особливого виду управління – антикризового. Мета дослідження
полягає у вивченні сучасних підходів науковців щодо сутності дефініцій «кризи», «кризових ситуацій»,
«антикризового управління», визначенні цілей та завдань антикризового управління, а також у
ґрунтовному аналізі етапів антикризового управління, основних антикризових стратегій, сучасних
моделей та методів прогнозування банкрутства. Проведене дослідження дозволило визначити власне
бачення сутності «кризи» як критичної ситуації, що загрожує стабільній діяльності підприємства і
вимагає прийняття управлінських рішень та заходів щодо її подолання. Кризова ситуація визначена як
різкий перехідний момент, що може призвести не тільки до кризового стану, а й настання кризи, що є
небезпечним для підприємства в сьогоденних умовах війни. Встановлено, що антикризове управління є
організованою системою управлінських рішень і дій, що забезпечує стабільну діяльність і розвиток
підприємства на основі використання ефективних методів, розроблення стратегій та заходів щодо
виявлення криз та їх подолання. Визначено сучасні методи та найпоширеніші економіко-математичні
моделі прогнозування банкрутства підприємства. Встановлено, що саме сьогодні під час війни ефективне
антикризове управління потребує розроблення та реалізації антикризових стратегій, здатних
забезпечити розвиток діяльності підприємства. Обґрунтовано необхідність упровадження в діяльність
підприємств антикризового управління на основі розроблення та реалізації сучасних антикризових
стратегій, таких, як «зростання», «розвиток цифрових технологій», оскільки саме такі стратегії
зможуть не тільки подолати кризу, а й забезпечити розвиток підприємства у майбутньому.In the current conditions of war and economic instability, it is extremely important in the activities
of any enterprise to respond to the emergence of crises that can lead to the development of a crisis state and even crises.
Therefore, modern leaders and managers need to timely identify possible sources of crisis phenomena, apply effective
tools to overcome them, and also introduce a special type of management into their activities – anti-crisis. The purpose
of the study is to study modern approaches of scientists to the essence of the definitions of «crisis», «crises», «anti-crisis
management», determine the goals and objectives of anti-crisis management, as well as in a thorough analysis of the
stages of anti-crisis management, the main anti-crisis strategies, modern models and methods of bankruptcy forecasting.
The conducted study allowed us to determine our vision of the essence of the «crisis» as a critical situation that threatens
the stable operation of the enterprise and requires the adoption of management decisions and measures to overcome it.
A crisis is defined as a sharp transition moment that can lead not only to a crisis state, but also to the onset of a crisis,
which is dangerous for an enterprise in the current conditions of war. It is established that anti-crisis management is an
organized system of management decisions and actions that ensures stable operations and development of an enterprise
based on the use of effective methods, development of strategies, and measures for identifying crises and overcoming
them. Modern methods and the most common economic and mathematical models for predicting the bankruptcy of an
enterprise are determined. It is established that today, during the war, effective anti-crisis management requires the
development and implementation of anti-crisis strategies that can ensure the development of the enterpriseʼs activities.
The need to introduce anti-crisis management into the activities of enterprises based on the development and
implementation of modern anti-crisis strategies such as «growth», «development of digital technologies» is
substantiated, since it is such strategies that will be able not only to overcome the crisis, but also to ensure the
development of the enterprise in the future
