scholarly journals Parametric Interaction of VLF and ELF Waves in the Ionosphere

2021 ◽  
Author(s):  
Vladimir I. Sotnikov
Keyword(s):  
Experimental Data ◽  
Wave Spectrum ◽  
Low Frequency ◽  
Parametric Interaction ◽  
Storm Activity ◽  
Very Low Frequency ◽  
Extremely Low Frequency ◽  
Space Experiments ◽  
Parametric Coupling ◽  
Vlf Waves

In this Chapter we analyze a non-linear parametric interaction between Very Low Frequency (VLF) and Extremely Low Frequency (ELF) waves in the ionosphere. We demonstrate that nonlinear parametric coupling between quasi-electrostatic Lower Oblique Resonance (LOR) and ELF waves significantly contributes to the VLF electromagnetic whistler wave spectrum. Analytical and numerical results are compared with experimental data obtained during active space experiments and satellite data. These data clearly show that presence of VLF waves in the region of plasmasphere boundary layer, where there are no injected due to substorm/storm activity energetic electrons with energies of tens keV can strongly affect the radiation belt boundary.

Mycotoxins in Coffee

1980 ◽  
Vol 63 (6) ◽  
pp. 1282-1285 ◽  
Author(s):  
Colette Levi
Keyword(s):  
Experimental Data ◽  
Low Frequency ◽  
Toxin Production ◽  
Green Coffee ◽  
Extremely Low Frequency ◽  
Mycotoxin Contamination ◽  
Green Coffee Beans ◽  
Coffee Beans ◽  
Roasting Process ◽  
Low Levels

Abstract This report reviews studies concerning the susceptibility of green coffee beans to mycotoxin contamination. Included are investigations on normal mold flora, toxin production in inoculated beans, effect of experimental roasting on aflatoxin, ochratoxin, and sterigmatocystin, and survey on the presence of these toxins in commercial green coffee. Because of the extremely low frequency of findings, the low levels of toxins, and the experimental data showing 70–80% destruction by the roasting process of toxin added to green coffee, further study on this topic has been discontinued.

scholarly journals Researches on very low frequency acoustic signal propagation characteristics in different shallow elastic wedge bottoms

2019 ◽  
Vol 283 ◽  
pp. 02003
Author(s):  
Jun Zhu ◽  
Hanhao Zhu ◽  
Jun Tang ◽  
Guangxue Zheng
Keyword(s):  
Acoustic Signal ◽  
Low Frequency ◽  
Signal Propagation ◽  
Acoustic Energy ◽  
Propagation Characteristics ◽  
The Finite Element Method ◽  
Very Low Frequency ◽  
Extremely Low Frequency ◽  
Elastic Bottom ◽  
Sloping Bottom

Targeted at the issue of extremely low-frequency (<100Hz) acoustic propagation in complex shallow elastic bottom environments. The influence law of different complex elastic bottoms on the acoustic signal propagation at very low frequency by acoustic energy flux has been analyzed with the simulation, which is based on the finite element method. The elastic bottoms which have been studied are the shallow horizontal elastic bottom, and the up-sloping and the down-sloping elastic bottom. The results show that the acoustic signal propagating in the up-sloping and down-sloping elastic bottom environments is more complex than that propagating in the horizontal elastic bottom, and the acoustic energy leaking into those elastic bottoms has very different influence on the acoustic signal propagation, especially in the up-sloping bottom.

scholarly journals Investigation of the Sudden Solar Ionospheric Disturbance using Radio Telescope

2020 ◽  
Vol 240 ◽  
pp. 07003
Author(s):  
Adam Aqasha ◽  
Andrien Zheng ◽  
Sneha Athreya ◽  
Hoe Teck Tan
Keyword(s):  
Solar Flares ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Ionospheric Disturbance ◽  
Low Frequency ◽  
The Sun ◽  
Radio Telescopes ◽  
Very Low Frequency ◽  
Set Up ◽  
Vlf Waves

Low-frequency radio telescopes are cheap and useful devices for the investigation of terrestrial and extra-terrestrial emissions. These emissions come either from the Sun and the planet Jupiter to terrestrial emissions. This project aims to investigate the Very Low Frequency (VLF) waves from mid-August to October 2019 using Radio JOVE (20 MHz) and SSID (3-30 kHz) to observe for the occurrence of solar flares and see how if the radio telescopes that the team set up is reliable. This will allow us future students aspiring to learn about astronomy to examine solar flares in detail during the upcoming solar maximum. Not many flares were detected as this period happens to be a solar minimum. However, a series of flares occurred between 30 September 2019 and 1 October 2019, which the telescopes have been able to detect, particularly SSID.

Psychophysiological Effects of Extremely Low Frequency Electromagnetic Fields: A Review

1973 ◽  
Vol 36 (3_suppl) ◽  
pp. 1131-1159 ◽  
Author(s):  
M. A. Persinger ◽  
H. W. Ludwig ◽  
K-P. Ossenkopp
Keyword(s):  
Experimental Data ◽  
Low Frequency ◽  
Geomagnetic Disturbances ◽  
Extremely Low Frequency ◽  
Magnetic Components ◽  
Wave Forms ◽  
Electrical Component ◽  
Power Densities ◽  
Cardiovascular Functions ◽  
Electrical Appliance

Extremely low frequency (ELF) electromagnetic field-waves, defined in this paper as occupying the frequency band of .01 to 100 Hz, are associated with geomagnetic disturbances, weather perturbations, electrical appliance discharges, and possibly seismic movements. ELF electromagnetic phenomena have been recorded as sinusoidal-like wave forms or as ELF pulses of short duration from higher frequency (10 to 100 kHz) waves. Although natural ELF electrical component intensities range from less than 1 mV/m to slightly more than 1 V/m with magnetic components less than a μ gauss and calculated power densities of 10−8 watts/m3, these waves can propagate long distances without appreciable attenuation and penetrate housing structures. Theoretically, it has been calculated that energy available from ELF phenomena can contribute to neuroenergetic functioning and protein-lipid activity. Correlational and experimental data indicate that ELF fields can influence reaction time, timing behavior, ambulatory behavior, oxygen uptake, endocrine changes, cardiovascular functions, and precipitation-clotting times of colloids. Possible mechanisms of ELF-organismic interactions are discussed.

Extremely low frequency detection of electrical discharges at Minamidake crater (Sakurajima volcano, Japan)

2020 ◽  
Author(s):  
Caron E.J. Vossen ◽  
Corrado Cimarelli ◽  
Alec J. Bennett ◽  
André Geisler ◽  
Damien Gaudin ◽  
...  
Keyword(s):  
Low Frequency ◽  
Japan Meteorological Agency ◽  
Frequency Range ◽  
Electrical Discharges ◽  
Very Low Frequency ◽  
Extremely Low Frequency ◽  
Sakurajima Volcano ◽  
Frequency Detection ◽  
The World ◽  
Active Volcanoes

&lt;p&gt;Volcanoes are increasingly better monitored around the world. Nonetheless, the detection and monitoring of volcanic ash plumes remains difficult, especially in remote areas. Intense electrical activity and lightning in volcanic plumes suggests that electrical monitoring of active volcanoes can aid the detection of ash emissions in near real-time. Current very low frequency and wide-band thunderstorm networks have proven to be able to detect plumes of large magnitude. However, the time delay and the relatively high number of non-detected explosive episodes show that the applicability of these systems to the detection of smaller (and often more frequent) ash-rich explosive events is limited. Here we use a different type of thunderstorm detector to observe electrical discharges generated by the persistent Vulcanian activity of Minamidake crater at Sakurajima volcano in Japan. The sensors consist of two antennas that measure the induced current due to the change in electric field with time. In contrast to the current thunderstorm networks, these sensors measure within the extremely low frequency range (1-45 Hz) and can detect lightning up to 35 kilometres distance.&lt;/p&gt;&lt;p&gt;Two detectors were installed at a distance of 3 and 4 kilometres from Minamidake crater and recorded almost continuously since July 2018. Within this period, the ash plumes reached a maximum height of 5.5 kilometres above the crater rim. Using a volcanic lightning detection algorithm and the catalogue of volcanic explosions compiled by the Japan Meteorological Agency (JMA), the number of electrical discharges was determined for each individual explosive event. In addition, the start of electrical discharges was compared to the eruption onset estimated by the JMA.&lt;/p&gt;&lt;p&gt;Preliminary results show that the detector closest to the crater had the highest detection efficiency. It detected electrical discharges during 60% of the eruptions listed by the JMA. This is significantly higher than for the World Wide Lightning Location Network, which detected electrical discharges (in the very low frequency range) within 20 kilometres of Sakurajima for less than 0.005% of the eruptions. Furthermore, the results show that for 40% of the detected eruptions, electrical discharges were detected before the estimated JMA timing. Hence, electrical discharges can mark the inception of the explosion with a higher precision and are an indication of ash emission. This demonstrates the value of the cost-effective sensors used here as a monitoring tool at active volcanoes.&lt;/p&gt;

SOURCE DISTANCE DEPENDENCE OF THE SURFACE‐IMPEDANCE CONDUCTIVITY MEASUREMENT TECHNIQUE

Geophysics ◽  
1969 ◽  
Vol 34 (5) ◽  
pp. 785-788 ◽  
Author(s):  
Peter R. Bannister
Keyword(s):  
Measurement Technique ◽  
Surface Impedance ◽  
Low Frequency ◽  
Conductivity Measurement ◽  
Very Low Frequency ◽  
Extremely Low Frequency ◽  
Source Distance ◽  
Distance Dependence ◽  
Magnetotelluric Method

The surface impedance conductivity measurement technique, commonly called the magnetotelluric method (Wait, 1962a), has been employed for many years at frequencies below 1 Hz. Recently, frequencies in the extremely low frequency (ELF) and very low frequency (VLF) bands have been employed (Watt et al, 1963).

scholarly journals The Influence of Solar Spectral Lines on Electron Concentration in Terrestrial Ionosphere

2011 ◽  
Vol 20 (4) ◽  
Author(s):  
A. Nina ◽  
V. Čadež ◽  
V. A. Srećković ◽  
D. Šulić
Keyword(s):  
Electron Concentration ◽  
Solar Flares ◽  
Low Frequency ◽  
Spectral Lines ◽  
Very Low Frequency ◽  
Phase Variations ◽  
Time Variations ◽  
Vlf Waves

AbstractOne of the methods of detection and analysis of solar flares is observing the time variations of certain solar spectral lines. During solar flares, a raise of electron concentration occurs in Earth’s ionosphere which results in amplitude and phase variations of the recorded very low frequency (VLF) waves. We compared the data obtained by the analysis of recorded VLF signals and line spectra for different solar flares. In this paper we treated the DHO VLF signal transmitted from Germany at the frequency of 23.4 kHz recorded by the AWESOME system in Belgrade (Serbia) during solar flares in the period between 10:40 UT and 13:00 UT on 2011 April 22.

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