scholarly journals Efficiency for Electron Acceleration in Solar Energy Release Region as Estimated in the Context of Plasma Mechanism of Radio Emission

1994 ◽  
Vol 142 ◽  
pp. 713-717
Author(s):  
B. N. Levin ◽  
V. M. Fridman ◽  
O. A. Sheiner
Keyword(s):  
Magnetic Trap ◽  
Inhomogeneous Plasma ◽  
Spectral Characteristics ◽  
Electron Acceleration ◽  
Plasma Radiation ◽  
Frequency Range ◽  
Superthermal Electrons ◽  
Radiation Mechanisms ◽  
Energy Release Region ◽  
Gyrosynchrotron Emission

AbstractThe paper is devoted to the interpretation of spectrographic data within the frequency range 8-12 GHz. Some spectral characteristics of weak solar steplike radio bursts are reported. To explain some parameters of the emission the ability to keep superthermal electrons in a magnetic trap with dense inhomogeneous plasma is theoretically studied. On the basis of this model we estimate the energy and number of accelerated electrons, and the flux density of precipitating electrons which are the source of enhanced plasma radiation. For the obtained efficiency of electron acceleration the calculated intensity of gyrosynchrotron emission proves to be less than the observed one.Subject headings: acceleration of particles — radiation mechanisms: nonthermal — Sun: flares — Sun: radio radiation

New aspects of power grid facilities personnel workplaces electromagnetic environment

2020 ◽  
Vol 60 (9) ◽  
pp. 569-574
Author(s):  
Nina B. Rubtsova ◽  
Sergey Yu. Perov ◽  
Olga V. Belaya ◽  
Tatiana A. Konshina
Keyword(s):  
Transmission Lines ◽  
Power Transmission ◽  
Power Grid ◽  
Spectral Characteristics ◽  
Ground Level ◽  
Frequency Characteristics ◽  
Frequency Range ◽  
Electromagnetic Environment ◽  
Limit Values ◽  
Special Assessment

Introduction. Electromagnetic safety of power grid facilities staff requires the exclusion of electromagnetic fields (EMF) harmful effects. EMF is evaluated by 50 Hz electric and magnetic fields (EF and MF) values in the framework of working conditions special assessment, and very rarely the analysis of the electromagnetic environment (EME) is carried out in depth. The aim of the study - EME hygienic assessment of power grid EHV facilities personnel workplace with adequate 50 Hz EF and MF levels evaluation as well as the analysis of EF and MF in the frequency range from 5 Hz to 500 Hz amplitude-frequency characteristics. Materials and methods. 50 Hz EF and MF values assessment was carried out on open switchgears (S) of substations and within sanitary breaks of 500 and 750 kV overhead power transmission lines (OTL). Measurements along to OTL trasses was performed using matrix-based method. Measurements and analysis of EF and MF values in 5-500 Hz frequency range amplitude-frequency characteristics were performed in the territory of 500 and 750 kV S. Results. Power frequency 50 Hz measurements results at 500 and 750 kV S ground-level personnel workplaces showed the presence of an excess of permissible limit values by EF intensity and the absence of an excess by MF. The measured EF values within 500 and 750 kV OTL sanitary gaps require limiting the working time of linemen due to the excess of the hygienic norms for full work shift, while the MP levels were almost completely within the standard values for persons not occupationally connected with electrical installations maintenance. MF and EE frequency range from 50 Hz to 500 Hz spectral characteristics analysis showed that 3rd harmonic percentage does not exceed 2.5% for EF and 6% for MF of the main level, the level of the 5th harmonic does not exceed 1% for EF and 3.5% for MF, the level of the 7th harmonic does not exceed 0.2% for EF and 0.8% for MF. These data show despite its low levels the contribution of MF different harmonics in a possible adverse impact on humane than EF corresponding harmonics. Conclusions. There was the confirmation of the previously justified use of the "matrix" scheme for of EF and MF values measurement along OTL routes. The relevance of to EF and MF all frequency components expos ure assessing possible health risk in extremely high voltage S territories and under OTL, based on international recommendations due to the lack of sanitary regulations in the Russian Federation for >50 Hz-30 kHz EF and MF, is shown.

scholarly journals Nonlinear analysis of decimetric solar bursts

2009 ◽  
Vol 5 (S264) ◽  
pp. 279-281
Author(s):  
Reinaldo R. Rosa ◽  
Mauricio J. A. Bolzan ◽  
Francisco C. R. Fernandes ◽  
H. S. Sawant ◽  
Marian Karlický
Keyword(s):  
Solar Radio ◽  
Inhomogeneous Plasma ◽  
Active Regions ◽  
Singularity Spectrum ◽  
Frequency Range ◽  
Radio Emissions ◽  
Magnetic Structures ◽  
Fine Structures ◽  
Solar Bursts ◽  
Solar Radio Emissions

AbstractThe solar radio emissions in the decimetric frequency range (above 1 GHz) are very rich in temporal and spectral fine structures due to nonlinear processes occurring in the magnetic structures on the corresponding active regions. In this paper we characterize the singularity spectrum, f(α), for solar bursts observed at 1.6, 2.0 and 3 GHz. We interpret our findings as evidence of inhomogeneous plasma turbulence driving the underlying plasma emission process and discuss the nonlinear multifractal approach into the context of geoeffective solar active regions.

scholarly journals Untangling cortico-striatal connectivity and cross-frequency coupling in L-DOPA-induced dyskinesia

2015 ◽  
Author(s):  
Jovana Belic ◽  
Per Halje ◽  
Ulrike Richter ◽  
Per Petersson ◽  
Jeanette Hellgren Kotaleski
Keyword(s):  
Primary Motor Cortex ◽  
Effective Connectivity ◽  
Spectral Characteristics ◽  
Low Frequency ◽  
Frequency Range ◽  
Gamma Frequency ◽  
High Gamma ◽  
Freely Behaving ◽  
Beta Frequency ◽  
Cross Frequency Coupling

We simultaneously recorded local field potentials in the primary motor cortex and sensorimotor striatum in awake, freely behaving, 6-OHDA lesioned hemi-parkinsonian rats in order to study the features directly related to pathological states such as parkinsonian state and levodopa-induced dyskinesia. We analysed the spectral characteristics of the obtained signals and observed that during dyskinesia the most prominent feature was a relative power increase in the high gamma frequency range at around 80 Hz, while for the parkinsonian state it was in the beta frequency range. Here we show that during both pathological states effective connectivity in terms of Granger causality is bidirectional with an accent on the striatal influence on the cortex. In the case of dyskinesia, we also found a high increase in effective connectivity at 80 Hz. In order to further understand the 80- Hz phenomenon, we performed cross-frequency analysis and observed characteristic patterns in the case of dyskinesia but not in the case of the parkinsonian state or the control state. We noted a large decrease in the modulation of the amplitude at 80 Hz by the phase of low frequency oscillations (up to ~10 Hz) across both structures in the case of dyskinesia. This may suggest a lack of coupling between the low frequency activity of the recorded network and the group of neurons active at ~80 Hz.

Spectra of quarry blasts and microearthquakes recorded at local distances in Israel

1993 ◽  
Vol 83 (6) ◽  
pp. 1799-1812
Author(s):  
Yefim Gitterman ◽  
Torild van Eck
Keyword(s):  
Time Delays ◽  
Spectral Characteristics ◽  
Open Pit ◽  
Frequency Range ◽  
Simple Method ◽  
Low Frequencies ◽  
Event Identification ◽  
Routine Basis ◽  
Seismograph Network ◽  
Discrimination Method

Abstract In northern Israel, quarry blasts and microearthquakes occur in a region with complicated tectonics. Therefore correct event identification, preferably based on a simple method that can be applied on a routine basis, is essential for accurate and detailed seismotectonic studies. Spectral analysis of quarry blasts and microearthquakes recorded at local distances (5 < Δ < 2000 km) by stations of the Israel Seismograph Network revealed spectral characteristics in the frequency range less than 12.5 Hz that can be used routinely for event identification. Most quarry blasts in northern Israel are ripple-fired, open pit blasts, consequently we chose an event discrimination method based on the recognition of ripple-firing patterns in the signal. A simple model for ripple firing parameters, based on interference theory of linear systems and including random effects, predicts spectral minima at low frequencies identical for different seismic phases. We compared the spectra of complete seismogram signals of 52 events recorded by the ISN at different distances and azimuths, including both microearthquakes and quarry blasts in a selected region of northern Israel. Consistent spectral modulation was found in a band from about 2 to 8 Hz for 18 of 21 reliably identified, i.e., reported, quarry blasts with time delays of 20 to 40 msec. The spectral minima frequencies correspond to those predicted by the theory.

scholarly journals Photo-ionized neon plasmas induced by radiation pulses of a laser-plasma EUV source and a free electron laser FLASH

2013 ◽  
Vol 31 (2) ◽  
pp. 195-201 ◽  
Author(s):  
A. Bartnik ◽  
R. Fedosejevs ◽  
P. Wachulak ◽  
H. Fiedorowicz ◽  
C. Serbanescu ◽  
...  
Keyword(s):  
Free Electron ◽  
Free Electron Laser ◽  
Extreme Ultraviolet ◽  
Spectral Characteristics ◽  
Emission Spectra ◽  
Spectral Lines ◽  
Plasma Radiation ◽  
Beam Radiation ◽  
Radiation Beam ◽  
Ionized Plasmas

AbstractIn this work, a laser-produced plasma extreme ultraviolet source and a free electron laser were used to create Ne photo-ionized plasmas. In both cases, a radiation beam was focused onto a gas stream injected into a vacuum chamber synchronously with the radiation pulse. Extreme ultraviolet radiation from the plasma spanned a wide spectral range with pronounced maximum centered at λ = 11 ± 1 nm while the free electron laser pulses were emitted at a wavelength of 32 nm. The power density of the focused plasma radiation was approximately 2 × 107 W/cm2 and was seven orders of magnitude lower compared with the focused free electron laser beam. Radiation fluences in both experimental conditions were comparable. Despite quite different spectral characteristics and extremely different power densities, emission spectra of both photo-ionized plasmas consist of the same spectral lines within a wavelength range of 20 to 50 nm, however, with different relative intensities of the corresponding lines. The dominating spectral lines originated from singly charged ions (Ne II); however, Ne III lines were also detected. Additionally, computer simulations of the emission spectra, obtained for photo-ionized plasmas, driven by the plasma extreme ultraviolet source, were performed. The corresponding measured and calculated spectra are presented. An electron temperature and ionic composition were estimated. Differences between the experimental spectra, obtained for both irradiation conditions, were analyzed. The differences were attributed mainly to different energies of driving photons.

Reflection of Conductive Plane Covered by Double Inhomogeneous Plasma Slab

2012 ◽  
Vol 229-231 ◽  
pp. 941-944
Author(s):  
Fei Yan ◽  
Zhong Cai Yuan ◽  
Yong Wang ◽  
Shi Lian Gong ◽  
Zheng Li
Keyword(s):  
Functional Dependence ◽  
Inhomogeneous Plasma ◽  
Plasma Electron ◽  
Reflection Coefficients ◽  
Frequency Range ◽  
Wide Range ◽  
Plasma Slab ◽  
Electromagnetic Signals ◽  
Set Up ◽  
Plasma Electron Density

This paper presents numerical results in the form of graphs of the power reflection coefficients for electromagnetic signals normally incident upon a conductive plane covered with two layers of inhomogeneous plasma slabs. The plasma electron density varies only in the direction perpendicular to the plane. Parameters considered in the computation cover a relatively wide range and the functional dependence of the power reflection coefficients on these parameters is studied. The results indicate that in a rather broad frequency range, the electromagnetic attenuations by the double slabs obviously excel the sum of attenuations resulted from two plasma layers when each layer exits respectively. The structure presented is easy to set up, which is instructive for plasma stealth.

Outstanding Stellar Microwave Flares in 1986

1987 ◽  
Vol 7 (1) ◽  
pp. 55-59 ◽  
Author(s):  
O. B. Slee ◽  
G. J. Nelson ◽  
R. T. Stewart ◽  
Alan E. Wright ◽  
David L. Jauncey ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Main Sequence ◽  
Relativistic Electrons ◽  
Spectral Indices ◽  
Frequency Range ◽  
High Brightness ◽  
Brightness Temperatures ◽  
Simultaneous Measurements ◽  
Gyrosynchrotron Emission ◽  
Large Frequency

AbstractWe describe bright microwave events that were first detected with the Parkes 64-m telescope at 8.4 or 22 GHz from six active-chromosphere stars. In some flares spectral data were obtained over a large frequency range from simultaneous measurements with the Parkes reflector (8.4 or 22 GHz), the Tidbinbilla interferometer (8.4 and 2.29 GHz), the Fleurs synthesis telescope (1.42 GHz) and the Molonglo Observatory synthesis telescope (0.843 GHz). Data on circular polarization were obtained from the Parkes observations at 8.4 GHz.The stars were in a wide variety of evolutionary states, ranging from a single pre-main-sequence star (HD 36705), two RS CVn binaries (HD 127535, HD 128171), an Algol (HD 132742) and two apparently single K giants (HD 32918 and HD 196818). Their high brightness temperatures, positive spectral indices and low polarization are consistent with optically thick gyrosynchrotron emission from mildly relativistic electrons with average energies 0.5 to 3 MeV gyrating in inhomogeneous magnetic fields of 5 to 100 G.

Analytical Approach to the Study of Circadian Leaf Oscillations in Clover. II. Responses to Continuous Light and to Sinusoidal Light Oscillations

1979 ◽  
Vol 6 (6) ◽  
pp. 673 ◽  
Author(s):  
GR Robinson ◽  
BIH Scott
Keyword(s):  
Analytical Approach ◽  
Spectral Characteristics ◽  
Continuous Light ◽  
Feedback Loops ◽  
Frequency Range ◽  
Constant Illumination ◽  
Two Phase ◽  
Rectangular Wave ◽  
Proposed Model ◽  
Trifolium Repens L

The spectral characteristics of the circadian leaf oscillation of Trifolium repens L. were investigated in constant illumination from 1-10 000 lux. The natural frequency was found to fall from 0.92 cycles/day at 1 lux to 0.84 cycles/day at 10 000 lux, with a corresponding fall in damping coefficient from 0.29 day-1 to 0.10 day-1. Spectral characteristics of the leaf responses to rectangular wave light variations, and to sinusoidal variations in the logarithm of light intensity were also compared. The response to sinusoidal light variations was measured over the frequency range 0.67-20 cycles/day and Bode amplitude and phase plots indicated resonances at 0.85 cycles/day (the circadian frequency) and also at 9.5 cycles/day. A model consisting of two feedback loops and two phase advance elements was developed and its frequency characteristics approximated to those of the leaf. The physiological implications of the proposed model are considered.

Wide Band Antenna with Ultra-smooth Spectral Characteristics

2021 ◽  
Vol 35 (11) ◽  
pp. 1292-1293
Author(s):  
Agaram Raghunathan ◽  
B. Girish ◽  
R. Somashekar ◽  
K. Srivani ◽  
Saurabh Singh ◽  
...  
Keyword(s):  
Spectral Characteristics ◽  
Wide Band ◽  
Antenna Design ◽  
Observational Cosmology ◽  
Spectral Signature ◽  
Spectral Features ◽  
Surface Currents ◽  
Frequency Range ◽  
Measurement Results ◽  
Frequency Independent

Understanding the evolution of Universe is, in the forefront of, the modern day observational cosmology. It requires precise and accurate measurement of cosmological signal, orders of magnitude weaker than the bright sky background. Detection of such a signal having distinct spectral signature, needs an antenna with frequency independent characteristics over more than an octave bandwidth. A spherical monopole antenna has been designed to operate in the frequency range 50-200 MHz with a spectral smoothness of about few parts in 104. The structure has been modeled and optimized using WIPL-D, to minimize spectral features arising out of abrupt reflections of surface currents and frequency dependent radiation patterns. A prototype has been built to validate the design. This paper presents the methodology adopted in the overall antenna design, experiences in its prototyping and simulation and the measurement results.

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