scholarly journals Researching of quasiperiodic variations in the amplitude of VLF electromagnetic signals from lightning discharges passing over strong earthquakes

2019 ◽  
Vol 127 ◽  
pp. 03005
Author(s):  
Vyacheslav Argunov ◽  
Mikhail Gotovtsev
Keyword(s):  
Lower Ionosphere ◽  
Signal Amplitude ◽  
Cross Sectional ◽  
Epicentral Area ◽  
F Region ◽  
Signal Characteristics ◽  
Lightning Discharges ◽  
Electromagnetic Signals ◽  
Wave Phenomena ◽  
Shallow Focus

The specific features of a method for radiosounding the lower ionosphere over earthquake epicenters using LF electromagnetic signals of thunderstorm sources (atmospherics) have been considered. The effects of shallow-focus earthquakes with magnitudes larger than 4.0 and their precursors manifest themselves in amplitude characteristics of atmospherics. It has been assumed that variations in the signal characteristics are related to disturbances in the lower ionosphere. According to the results of azimuthal scanning, cross sectional dimensions of disturbed regions, as a rule, correspond to the dimensions of the first two Fresnel zones for signals at a frequency of 10 kHz. Azimuthal scanning also indicated that the positions of disturbed regions during and before earthquakes could have a certain dynamics and differ from the projection onto the earthquake epicenter. Quasi-periodic variations of signal amplitude of lightning discharges passing over earthquake epicenters are in details considered. It has been obtained that the period of amplitude modulation makes up 2-3 hours, i.e. in the ionosphere D-layer the same values of the periods of wave phenomena are registered as which are observed in a higher F-region of the ionosphere. The results obtained during the work specify that, at least, in the part of events the seismic disturbances in the ionosphere can be caused by AGW, propagating upwards from the epicentral area.

Determine the Physical Mechanism and Source Region of Beat Wave Modulation by Changing the Frequency of HF Waves

2021 ◽  
Author(s):  
Zhe Guo ◽  
Hanxian Fang ◽  
Farideh Honary
Keyword(s):  
Physical Mechanism ◽  
Source Region ◽  
Low Frequency ◽  
Signal Amplitude ◽  
New Approach ◽  
Wave Modulation ◽  
F Region ◽  
Source Regions ◽  
High Modulation ◽  
E Region

Abstract This paper introduces a new approach for the determination of the source region of BW (beat wave) modulation. This type of modulation is achieved by transmitting HF continuous waves with a frequency difference of f, where f is the frequency of modulated ELF/VLF (extremely low frequency/very low frequency) waves from two sub-arrays of a high power HF transmitter. Despite the advantages of BW modulation in terms of generating more stable ELF/VLF signal and high modulation efficiency, there exists a controversy on the physical mechanism of BW and its source region. In this paper, the two controversial theories, i.e. BW based on D-E region thermal nonlinearity and BW based on F region ponderomotive nonlinearity are examined for cases where each of these two theories exists exclusively or both of them exist simultaneously. According to the analysis and the simulation results presented in this paper, it is found that the generated VLF signal amplitude exhibits significant variation as a function of HF frequency in different source regions. Therefore, this characteristic can be utilised as a potential new approach to determine the physical mechanism and source location of BW.

scholarly journals Highly Directive Biconic Antennas Embedded in a Dielectric

2020 ◽  
Vol 10 (24) ◽  
pp. 8828
Author(s):  
Alessandro Chiolerio ◽  
Lorenzo Diazzi ◽  
Daniele Funaro
Keyword(s):  
Power Transmission ◽  
Dielectric Material ◽  
Communication Channels ◽  
Extended Model ◽  
Wireless Power ◽  
Speed Of Light ◽  
Straight Line ◽  
Electromagnetic Signals ◽  
Point To Point ◽  
Wave Phenomena

Designing antennas suitable for generating highly directive electromagnetic signals has become a fundamental task. This is particularly relevant for the development of efficient and sustainable point-to-point communication channels, and for energy transfer. Indeed, these are nowadays expanding areas of research. In order to deal with said particular wave phenomena, an extension of the electrodynamics equations is taken into account, where exact solitonic type solutions are admitted. These waves may have compact support and travel along a straight line, without dissipation, at the speed of light. The result suggests the design of biconic type antennas having specific properties that are numerically examined in this paper. The cones, supplied with an oscillating source, are embedded in a dielectric material of suitable shape, with the purpose of driving the signal in the proper direction. The computations based on the extended model are aimed toward simulating the possibility of generating peculiar wave behaviors, in view of practical implementations in the framework of point-to-point communications or wireless power transmission.

P1005Origin, distribution and timing of the slow pathway potentials recorded inside the Kock's triangle in Avnrt patients through High-density Mapping

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
L Segreti ◽  
C Lavalle ◽  
M Galeazzi ◽  
G Zingarini ◽  
M G Bongiorni ◽  
...  
Keyword(s):  
Signal Amplitude ◽  
Slow Pathway ◽  
Atrioventricular Nodal Reentrant Tachycardia ◽  
High Type ◽  
Density Mapping ◽  
Signal Characteristics ◽  
Mapping System ◽  
Variable Distribution ◽  
Atrial Activation ◽  
Reentrant Circuit

Abstract Background Atrial activation during typical atrioventricular nodal reentrant tachycardia (AVNRT) exhibits anatomic variability and spatially heterogeneous propagation inside the Kock's Triangle (KT). The mechanism of the reentrant circuit has not been elucidated yet. Purpose To evaluate signal characteristics and find out the origin, distribution, and timing of the slow pathway (SP) potentials recorded in the KT. Methods The 3-D KT geometry was created during both sinus rhythm (SR) and tachycardia (TR) from the basket mapping catheter IntellaMap Orion and the Rhythmia Mapping System (Boston Scientific). The KT was divided into 8 regions moving from an antero-septal to postero-septal areas and bounded by tricuspid annulus (TA) anteriorly and tendon of Todaro (TT) posteriorly. Each area was characterized in terms of distribution and timing of Jackman (JP) and Haissaguerre (HP) potentials and signal amplitude. Results 20 consecutive successful SP ablation cases of AVNRT were included (mean RA acquired points = 6000±1100, 275±63 inside the KT; mean KT area=29±3mm2; mean mapping time=12±5 minutes). During SR, the site of earliest atrial activation within the KT was anterior in 80% of patients whereas a midseptal activation occurred less frequently (20%). The mid-septal regions bounded by TA anteriorly and TT posteriorly showed higher prevalence of JP as compared to antero-/mid-septal regions across TT both in SR and TR (77.4% vs 4.8% during SR, p<0.0001; 84.1% vs 0% during TR, p<0.0001, respectively). HPs seemed to have variable distribution across KT (50% of these potentials recorded in antero- to mid-septal regions across TT for SR, 52.3% for TR). The median signal voltage was 0.44 [0.2–0.9] mV during SR and 0.5 [0.22–0.895] mV during TR. The mid-septal region was the area of lowest voltage compared to other regions (0.2 [0.1–0.7] mV vs 0.5 [0.4–1.5] mV for SR, p<0.0001; 0.2 [0.15–0.6] mV vs 0.6 [0.4–1.5] mV for TR, p<0.0001, respectively). Conclusion JPs seem to be associated with low signal-amplitude areas whereas HPs seem to have variable distribution across KT. Although not perfectly known, the typical low-high-type double potential of JP might be therefore explained by wavefront collision in the lowest area of the KT. Acknowledgement/Funding None

scholarly journals Meteorological effects in the lower ionosphere as based on VLF/LF signal observations

2014 ◽  
Vol 2 (4) ◽  
pp. 2789-2812 ◽  
Author(s):  
A. Rozhnoi ◽  
M. Solovieva ◽  
B. Levin ◽  
M. Hayakawa ◽  
V. Fedun
Keyword(s):  
Gravity Waves ◽  
Atmospheric Pressure ◽  
Low Frequency ◽  
Lower Ionosphere ◽  
Signal Amplitude ◽  
Internal Gravity Waves ◽  
Atmospheric Parameters ◽  
Low Latitudes ◽  
Far Eastern ◽  
Meteorological Effects

Abstract. Very low and low frequency (VLF/LF) data recorded in the Far Eastern stations Petropavlovsk-Kamchatsky (158.92° E, 53.15° N), Yuzhno-Sakhalinsk (142.75° E, 46.95° N) and Yuzhno-Kurilsk (145.861° E, 44.03° N) are investigated to study the meteorological effects in the lower ionosphere. The results demonstrate the sensitivity of the VLF/LF signals to the variations of atmospheric pressure, humidity, wind velocity and temperature, and the VLF/LF record at the station of Yuzhno-Kurilsk is found to be most sensitive to those variations of atmospheric parameters. The region under consideration is characterized by high winter cyclonic activity in midlatitudes and strong summer and autumn typhoon activity in low latitudes. VLF/LF signal variations during 8 tropical cyclones (TCs) with different intensity are considered. Negative nighttime anomalies in the signal amplitude that are most probably caused by TC activity are found for 6 events. Those anomalies are observed during 1–2 days when TCs move inside the sensitivity zones of the subionospheric paths. Perturbations of the VLF signal observed during 2 TCs can be caused by both the TC influence and seismic activity, but no correlation between TC intensity and magnitude of the signal anomalies is found. Spectral analysis of the typhoon-induced disturbed signals revealed the fluctuations with time periods in the range of 7–16 and 15–55 min that corresponds to the range of internal gravity waves periods.

scholarly journals Remote sensing and modeling of energetic electron precipitation into the lower ionosphere using VLF/LF radio waves and field aligned current data

2015 ◽  
Vol 13 ◽  
pp. 233-242
Author(s):  
E. D. Schmitter
Keyword(s):  
Distribution Function ◽  
Energetic Electron ◽  
Lower Ionosphere ◽  
Signal Amplitude ◽  
Reaction Rates ◽  
Current Data ◽  
Electron Precipitation ◽  
Propagation Path ◽  
Satellite Mission ◽  
Field Aligned Current

Abstract. A model for the development of electron density height profiles based on space time distributed ionization sources and reaction rates in the lower ionosphere is described. Special attention is payed to the definition of an auroral oval distribution function for energetic electron energy input into the lower ionosphere based on a Maxwellian energy spectrum. The distribution function is controlled by an activity parameter which is defined proportional to radio signal amplitude disturbances of a VLF/LF transmitter. Adjusting the proportionality constant allows to model precipitation caused VLF/LF signal disturbances using radio wave propagation calculations and to scale the distribution function. Field aligned current (FAC) data from the new Swarm satellite mission are used to constrain the spatial extent of the distribution function. As an example electron precipitation bursts during a moderate substorm on the 12 April 2014 (midnight–dawn) are modeled along the subauroral propagation path from the NFR/TFK transmitter (37.5 kHz, Iceland) to a midlatitude site.

scholarly journals Virgins are Louder: The Effect of Mating on Acoustic Signaling in Sagebrush Crickets

1995 ◽  
Vol 19 ◽  
pp. 78-83
Author(s):  
W. Snedden ◽  
Michael Greenfield
Keyword(s):  
Hind Wing ◽  
Spectral Characteristics ◽  
Signal Amplitude ◽  
Surgical Excision ◽  
Male Mating ◽  
Acoustic Signaling ◽  
Signal Characteristics ◽  
Before And After ◽  
Virgin Male ◽  
Cyphoderris Strepitans

Female sagebrush crickets, Cyphoderris strepitans, feed on the male's hind wings during copulation. Because removal of hind wing material during mating may alter male acoustic signal characteristics and account for a virgin male mating advantage (Morris et al. 1989; Snedden, in press) we recorded virgin and mated males in the field, and virgins before and after surgical excision of a portion of the hind wings. We found no significant differences in signal spectral characteristics or pulse rate between virgin and mated males following hind­wing excision. However, the signal amplitude of laboratory recorded virgins was greater than that of mated males, and song amplitude was reduced in manipulated males. In contrast, signal amplitude was lower in field recorded virgins than mated males.

The Quebec–Maine Border Earthquake, 15 June 1973

1975 ◽  
Vol 12 (11) ◽  
pp. 1917-1928 ◽  
Author(s):  
R. J. Wetmiller
Keyword(s):  
New England ◽  
Focal Mechanism ◽  
Appalachian Mountains ◽  
Strike Slip ◽  
Maximum Intensity ◽  
Focal Mechanism Solution ◽  
Epicentral Area ◽  
Eastern Ontario ◽  
Shallow Focus ◽  
Strike Slip Movement

On 15 June 1973, a shallow-focus earthquake with magnitude mb 4.8 occurred in southern Quebec, in an area that has a record of only a few minor earthquakes during the previous 200 years. This event was felt throughout southern Quebec, eastern Ontario, and the New England States, to a distance of 300 km from the epicenter. A small amount of minor damage to plaster and chimneys occurred in the immediate epicentral area, indicating a maximum intensity of VI. The focal mechanism solution suggests that the earthquake was the result of primarily strike-slip movement along a plane trending northeast or a plane trending northwest. Arguments are presented that this event is part of the seismicity associated with the northern Appalachian Mountains.

Sign in / Sign up

Export Citation Format

Share Document