scholarly journals Multipoint observations of Ionospheric Alfvén Resonance

2016 ◽  
Vol 6 (1) ◽  
pp. 45-49 ◽  
Author(s):  
N. Baru ◽  
A. Koloskov ◽  
Y. Yampolsky ◽  
R. Rakhmatulin
Keyword(s):  
Low Frequency ◽  
Solar Observatory ◽  
Resonance Structure ◽  
Data Series ◽  
Annual Data ◽  
The Earth ◽  
Electromagnetic Resonances ◽  
Global Nature ◽  
Propagation Medium ◽  
Magnetic Station

Among the processes that form properties of the geospace in the circumterrestrial plasma the electromagnetic resonances of the Earth, such as Schummann Resonance (SR) and Ionospheric Alfvén Resonance (IAR) are of great importance. IAR is more localized in space than SR and its properties largely depend on the characteristics of the propagation medium. In contrast to the SR, which has global nature and which is continuously observable at any time of the day, IAR signals are registered mostly during the nighttime and demonstrate more variability of the parameters than SR signals. At the Earth surface IAR is registered as Spectral Resonance Structure of the natural electromagnetic noise at frequency range 0.1-40 Hz. In this work we studied an influence of the environment characteristics on IAR parameters by the means of multipoint observations. Annual data series recorded at Ukrainian Antarctic Station 'Akademik Vernadsky', Low Frequency Observatory of the Institute of Radio Astronomy near Kharkov (Ukraine) and magnetic station of Sayan Solar Observatory Mondy near Irkutsk (Russia) were used for the analysis. We investigated the behaviour of IAR parameters, such as probability of resonance lines registration and frequency spacing $\Delta F$, for annual and diurnal intervals. These parameters were compared with characteristics of the ionosphere above all of the observation points and geomagnetic activity.

Schumann resonance intensity as a precursor for warm ENSO episodes

2020 ◽  
Author(s):  
Gabriella Satori ◽  
Tamas Bozoki ◽  
Earle Williams ◽  
Colin Price ◽  
Anirban Guha ◽  
...  
Keyword(s):  
Low Frequency ◽  
Intensity Variation ◽  
Lightning Activity ◽  
Medium Size ◽  
Percentage Increase ◽  
Efficient Tool ◽  
Schumann Resonances ◽  
The Earth ◽  
Electromagnetic Resonances ◽  
Systematic Behavior

<p>Schumann resonances (SR) are the global electromagnetic resonances of the Earth-ionosphere cavity and constitute the extremely low frequency (< 100 Hz) radiation of the worldwide lightning activity (Schumann, 1952). The recording of SR intensity at a few distant SR stations is an efficient tool to monitor the global lightning. We present the variations of SR intensity in the transition months preceding the warm ENSO episodes for the two super El Niño events in 1997/98 and 2015/16 as well as for the two medium size El Niño periods in 2001/02 and 2008/09  based on SR observations at multiple locations.: Nagycenk, Hungary (47.6N, 16.7E);  Hornsund, Svalbard (77.0N, 15.6E);  Eskdalemuir, UK (55.3N, 3.2W);  Alberta, Canada (51.9N, 111.5W);  Boulder Creek, USA (37.2N, 122.1W).</p><p>A remarkable increase in SR intensity is documented two-three months before or just at the beginning of El Niño episodes as compared with the SR intensity in the same months of the preceding La Niña (or non-ENSO) phase for all cases studied here. The percentage increase in SR intensity depends on the amplitude of the warm ENSO period, and is consistently higher for the two super El Niño events. The enhanced SR intensity indicates a worldwide response of global lightning activity. Increased atmospheric instability due to the land-ocean thermal interaction during the transition interval could be responsible for the intensification of lightning activity. This systematic behavior may have been overlooked in earlier studies that compared lightning activity in the integrated ‘cold’ and the ‘warm’ phases, but without exploring the transitional variation. Our results suggest that the SR intensity variation on the interannual time scale acts a precursor for the occurrence of warm ENSO episode.</p>

scholarly journals Temporal Variations of the Turbulence Profiles at the Sayan Solar Observatory Site

Atmosphere ◽  
2019 ◽  
Vol 10 (9) ◽  
pp. 499 ◽  
Author(s):  
Artem Shikhovtsev ◽  
Pavel Kovadlo ◽  
Vladimir Lukin
Keyword(s):  
Atmospheric Turbulence ◽  
Temporal Variability ◽  
Low Frequency ◽  
Temporal Variations ◽  
Solar Observatory ◽  
Vertical Profiles ◽  
Spatial And Temporal Scales ◽  
Atmospheric Disturbances ◽  
Wide Range ◽  
The Mean

The paper focuses on the development of the method to estimate the mean characteristics of the atmospheric turbulence. Using an approach based on the shape of the energy spectrum of atmospheric turbulence over a wide range of spatial and temporal scales, the vertical profiles of optical turbulence are calculated. The temporal variability of the vertical profiles of turbulence under different low-frequency atmospheric disturbances is considered.

Foreshock ULF fluctuations near the Moon: THEMIS observations

2021 ◽  
Author(s):  
Anna Salohub ◽  
Jana Šafránková ◽  
Zdeněk Němeček
Keyword(s):  
Solar Wind ◽  
Rest Frame ◽  
Low Frequency ◽  
Solar Wind Plasma ◽  
Turbulent Plasma ◽  
Bow Shock ◽  
Ulf Waves ◽  
The Moon ◽  
Shock Surface ◽  
The Earth

<p>The foreshock is a region filled with a turbulent plasma located upstream the Earth’s bow shock where interplanetary magnetic field (IMF) lines are connected to the bow shock surface. In this region, ultra-low frequency (ULF) waves are generated due to the interaction of the solar wind plasma with particles reflected from the bow shock back into the solar wind. It is assumed that excited waves grow and they are convected through the solar wind/foreshock, thus the inner spacecraft (close to the bow shock) would observe larger wave amplitudes than the outer (far from the bow shock) spacecraft. The paper presents a statistical analysis of excited ULF fluctuations observed simultaneously by two closely separated THEMIS spacecraft orbiting the Moon under a nearly radial IMF. We found that ULF fluctuations (in the plasma rest frame) can be characterized as a mixture of transverse and compressional modes with different properties at both locations. We discuss the growth and/or damping of ULF waves during their propagation.</p>

WORKING DEPTHS FOR LOW FREQUENCY ELECTRICAL PROSPECTING

Geophysics ◽  
1945 ◽  
Vol 10 (1) ◽  
pp. 63-75 ◽  
Author(s):  
William Bradley Lewis
Keyword(s):  
Low Frequency ◽  
Electrical Measurements ◽  
The Earth ◽  
Electrical Prospecting

Electrical measurements were made on the surface of the earth with low frequency commutated current using nineteen separate frequencies and six electrode separations. Analysis of the data indicates that there is an effect of appreciable magnitude attributable to an interface 6000 feet below the surface.

scholarly journals Precision Pulsar Timing with NASA's Deep Space Network

2015 ◽  
Vol 11 (A29B) ◽  
pp. 367-369
Author(s):  
Lawrence Teitelbaum ◽  
Walid Majid ◽  
Manuel M. Franco ◽  
Daniel J. Hoppe ◽  
Shinji Horiuchi ◽  
...  
Keyword(s):  
Low Frequency ◽  
Radio Waves ◽  
Deep Space ◽  
Radio Pulsars ◽  
Deep Space Network ◽  
Space Network ◽  
The Earth ◽  
Pulsar Timing ◽  
Initial Results ◽  
Stable Rotation

AbstractMillisecond pulsars (MSPs) are a class of radio pulsars with extremely stable rotation. Their excellent timing stability can be used to study a wide variety of astrophysical phenomena. In particular, a large sample of these pulsars can be used to detect low-frequency gravitational waves. We have developed a precision pulsar timing backend for the NASA Deep Space Network (DSN), which will allow the use of short gaps in tracking schedules to time pulses from an ensemble of MSPs. The DSN operates clusters of large dish antennas (up to 70-m in diameter), located roughly equidistant around the Earth, for communication and tracking of deep-space spacecraft. The backend system will be capable of removing entirely the dispersive effects of propagation of radio waves through the interstellar medium in real-time. We will describe our development work, initial results, and prospects for future observations over the next few years.

scholarly journals Geomagnetism, volcanoes, global climate change, and predictability. A progress report

1994 ◽  
Vol 37 (5 Sup.) ◽  
Author(s):  
G. P. Gregori
Keyword(s):  
State Of The Art ◽  
Global Climate ◽  
Data Series ◽  
Theoretical Studies ◽  
Data Handling ◽  
Future Perspectives ◽  
Proxy Data ◽  
Interstellar Clouds ◽  
The Earth ◽  
Glacier Melting

A model is investigated, by which the encounters of the solar system with dense interstellar clouds ought to trigger either geomagnetic field reversals or excursions, that produce extra electric currents within the Earth dynamo, that cause extra Joule's heating, that supplies volcanoes and endogenous processes. Volcanoes increase the Earth degassing into the atmosphere, hence the concentration of the minor atmospheric constituents, including the greenhouse gases, hence they affect climate temperature, glacier melting, sea level and global change. This investigation implies both theoretical studies and observational data handling on different time scales, including present day phenomena, instrumental data series, historical records, proxy data, and geological and palaeontological evidences. The state of the art is briefly outlined, mentioning some already completed achievements, investigations in progress, and future perspectives.

scholarly journals Structural attributes of firms, irreversibility, and uncertainty of corporate investment in Nigeria

2021 ◽  
Vol 18 (3) ◽  
pp. 397-407
Author(s):  
Jonathan Oniovosa Ososuakpor
Keyword(s):  
Exchange Rate ◽  
Stock Exchange ◽  
Exchange Rate Volatility ◽  
Corporate Investment ◽  
Negative Influence ◽  
Data Series ◽  
Annual Data ◽  
Corporate Investments ◽  
Investment Projects ◽  
Macroeconomic Uncertainty

In the Nigerian context, there is a gap in the literature on the structural attributes of firms and the extent to which corporate investments are irreversible. Thus, this study was to empirically examine the structural attributes of firms, irreversibility, and uncertainty of corporate investment using the real options theory of investment. The study is based on annual data series of firms listed on the Nigerian Stock Exchange from 2005 to 2019. The study measured structural attributes using competitiveness and monopoly/oligopoly of a firm, macroeconomic uncertainty, inflation, interest, and exchange rates, and examines their association with corporate investments. The study was conducted using a panel dataset adopting a fixed-effect estimation technique that takes into account potential endogeneity and firm specific-effects. The result showed that the macroeconomic uncertainty measure of exchange rate volatility is strongly detrimental to corporate investment decisions. Furthermore, interest rate and inflation volatilities are not detrimental to investment growth, while exchange rate uncertainty has a substantial negative influence on corporate investment. Besides, macroeconomic uncertainty was found to be a greater disincentive for firms with irreversible investments than for firms with more easily reversible investment projects.

scholarly journals Effects of temperature variations in high-sensitivity Sagnac gyroscope

2021 ◽  
Vol 136 (5) ◽  
Author(s):  
Andrea Basti ◽  
Nicolò Beverini ◽  
Filippo Bosi ◽  
Giorgio Carelli ◽  
Donatella Ciampini ◽  
...  
Keyword(s):  
Earth Rotation ◽  
Mechanical Design ◽  
Low Frequency ◽  
Environmental Parameters ◽  
High Sensitivity ◽  
Rotation Axes ◽  
The Earth ◽  
Sagnac Gyroscope ◽  
Laser Gyroscopes

AbstractGINGERINO is one of the most sensitive Sagnac laser-gyroscopes based on an heterolithic mechanical structure. It is a prototype for GINGER, the laser gyroscopes array proposed to reconstruct the Earth rotation vector and in this way to measure General Relativity effects. Many factors affect the final sensitivity of laser gyroscopes, in particular, when they are used in long-term measurements, slow varying environmental parameters come into play. To understand the role of different terms allows to design more effective mechanical as well as optical layouts, while a proper model of the dynamics affecting long-term (low frequency) signals would increase the effectiveness of the data analysis for improving the overall sensitivity. In this contribution, we focus our concerns on the effects of room temperature and pressure aiming at further improving mechanical design and long-term stability of the apparatus. Our data are compatible with a local orientation changes of the Gran Sasso site below $$\mu $$ μ rad as predicted by geodetic models. This value is consistent with the requirements for GINGER and the installation of an high-sensitivity Sagnac gyroscope oriented at the maximum signal, i.e. along the Earth rotation axes.

Sign in / Sign up

Export Citation Format

Share Document