Comparison of Q-bursts detected near the Earth’s surface and 140 m below ground level

2021 ◽  
Author(s):  
József Bór ◽  
István Lemperger ◽  
Karolina Szabóné André ◽  
Tamás Bozóki ◽  
Janusz Mlynarczyk ◽  
...  
Keyword(s):  
Wave Attenuation ◽  
Low Frequency ◽  
Field Measurements ◽  
Ground Level ◽  
Finite Conductivity ◽  
Radio Waves ◽  
Radio Communication ◽  
Mine Shaft ◽  
Near Surface ◽  
The Earth

<p>Q-bursts are signatures of exceptionally powerful lightning strokes which produce intense radio waves typically in the extremely low frequency band (ELF, 3Hz-3kHz). Due to the finite conductivity of the Earth’s surface, radio waves in this frequency range can be also detected in greater depths. While the penetration of electromagnetic (EM) waves in a conducting half space has been investigated and utilized, e.g., under water for submarine radio communication, very few field measurements consider the subsurface detection of ELF waves in the continental crust.</p><p>In this work, Q-bursts recorded in near surface and corresponding underground ELF band observations are compared in order to characterize the frequency dependent effect of the upper section of the Earth’s crust on the spectrum of the Q-burst signals.</p><p>Practically co-located, but not simultaneous quasi-surface and underground temporal ELF band magnetic field measurements were made near Mátraszentimre, in the Mátra Mountains, Hungary. The underground measurement was carried out inside a mine shaft in the Matra Gravitational and Geophysical Laboratory (MGGL) at a depth of 140 m. ELF observations from two permanent recording stations in the Széchenyi István Geophysical Observatory (NCK, Hungary) and in Hylaty (HYL, Poland), less than 250 km away from MGGL, were involved in the analysis to deduce the transfer function between the unsynchronized quasi-surface and underground measurements in the Mátra.</p><p>The set of Q-bursts, which were parallelly detected at all three locations, was identified using GPS synchronized time stamps. Natural origin of the signals was confirmed by identifying the parent lightning strokes in the database of the World Wide Lightning Location Network (WWLLN) via matching the detection times and the corresponding source directions calculated at NCK station.</p><p>The good agreement of the results from independent Matra-NCK (5-30 Hz) and Matra-HYL (5-140 Hz) station-pairwise analyses confirm that the frequency dependence of the wave attenuation due to overlying rocks is exponential. The deduced integrated local conductivity, 30-40 S/m, of the upper section of the Earth’s crust suggests that probably the soil has prominent role in attenuating ground penetrating EM waves in the ELF band.</p>

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.

The ionosphere as a whispering gallery

1962 ◽  
Vol 265 (1323) ◽  
pp. 554-569 ◽  
Keyword(s):  
Electron Density ◽  
Spherical Surface ◽  
Low Frequency ◽  
Electron Density Profile ◽  
Whispering Gallery Modes ◽  
Radio Waves ◽  
Sound Waves ◽  
Whispering Gallery ◽  
The Earth ◽  
Reflexion Coefficient

The propagation of radio waves of very low frequency to great distances is conveniently treated by regarding the space between the earth and the ionosphere as a wave-guide. Several authors have found that the least attenuated modes are profoundly affected by the earth’s curvature. This effect is investigated for several models of the ionosphere. It is found, in particular, that for frequencies greater than about 30 kc/s some modes are possible for which the energy is concentrated in a region near the base of the ionosphere, and the field strength near the ground is small. It is useful to think of such modes as being composed of waves repeatedly reflected at the inside spherical surface of the ionosphere, the rays being chords of this sphere. By analogy with sound waves these modes are called ‘whispering gallery modes’. The theory uses wave admittance and reflexion coefficient variables because these satisfy differential equations which are convenient for integration using a digital computer. The curvature of the earth is allowed for by using the method of the modified refractive index, but the earth’s magnetic field is neglected. Formulae for the m ode condition and the excitation of the various modes by a transmitter are given and discussed. A new way of dealing with an ionosphere having a continuous electron density profile is presented. The results of some numerical calculations are given both for a sharply bounded homogeneous ionosphere and for an exponential profile of electron density.

scholarly journals Spatial and Temporal Distribution of Modified Radio Refractivity Gradient at 875 hPa and 700 hPa over Nigeria

2019 ◽  
pp. 1-13
Author(s):  
S. E. Falodun ◽  
J. S. Ojo ◽  
V. O. Oviangbede
Keyword(s):  
Communication Systems ◽  
Coastal Region ◽  
Temporal Distribution ◽  
Weather Forecast ◽  
Ground Level ◽  
Radio Waves ◽  
Radio Communication ◽  
Night Time ◽  
Medium Range Weather Forecast ◽  
Seasonal Basis

The meteorological effects on radio wave signals propagating through the troposphere are of great concerns in the design and performance of radio communication systems. Often, the effect can lead to anomalous propagation conditions such as ducting, super refraction and sub refraction. In this paper, the spatial-temporal distribution of modified radio refractivity gradient and the effects on radio waves propagating at 875 hPa and 700 hPa pressure levels over sixteen selected locations aloft the four climatic regions of Nigeria are investigated. Five (5) years (2013-2017) meteorological parameters namely: air temperature, relative humidity and atmospheric pressure at ground level and 1 km above ground level were obtained from the European Center for Medium-Range Weather Forecast (ECMWF) at four synopses hours of the day. Modified radio refractivity and its gradient at the two pressure levels were computed using ITU- model. Results on a daily and seasonal basis shows similar trends at both 875 hPa and 700 hPa pressure levels, with higher values of modified radio refractivity gradient recorded at 700 hPa heights at the morning and night hours of the day. Results on seasonal basis shows that during the rainy season, modified radio refractivity gradients were high. On location basis, Port Harcourt (coastal region) recorded the highest value of modified radio refractivity gradient of about 115.5 M-units/km in the night time (00:00 hr. LT). The value depicts the occurrence of normal refraction in this location. The overall results will be useful for microwave links budgeting and design in Nigeria.

scholarly journals Satellite Measured Ionospheric Magnetic Field Variations over Natural Hazards Sites

2021 ◽  
Vol 13 (12) ◽  
pp. 2360
Author(s):  
Christoph Schirninger ◽  
Hans U. Eichelberger ◽  
Werner Magnes ◽  
Mohammed Y. Boudjada ◽  
Konrad Schwingenschuh ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Natural Hazards ◽  
Field Measurements ◽  
Volcanic Eruptions ◽  
Low Earth Orbit ◽  
Near Surface ◽  
The Earth ◽  
Magnetic Field Measurements ◽  
Spatio Temporal ◽  
Magnetic Field Variations

Processes and threats related to natural hazards play an important role in the evolution of the Earth and in human history. The purpose of this study is to investigate magnetic field variations measured at low Earth orbit (LEO) altitudes possibly associated with earthquakes, volcanic eruptions, and artificial outbursts. We focus on two missions with well equipped magnetometer packages, the China Seismo-Electromagnetic Satellite (CSES) and ESA’s three spacecraft Swarm fleet. After a natural hazards survey in the context of this satellites, and consideration of external magnetospheric and solar influences, together with spacecraft interferences, wavelet analysed spatio-temporal patterns in ionospheric magnetic field variations related to atmospheric waves are examined in detail. We provide assessment of the links between specific lithospheric or near surface sources and ionospheric magnetic field measurements. For some of the diverse events the achieved statistical results show a change in the pattern between pre- and post-event periods, we show there is an increase in the fluctuations for the higher frequency (smaller scales) components. Our results are relevant to studies which establish a link between space based magnetic field measurements and natural hazards.

Omega Navigation in the Shadow of Antarctica

1989 ◽  
Vol 42 (2) ◽  
pp. 236-247
Author(s):  
R. Barr ◽  
K. B. Young
Keyword(s):  
Northern Hemisphere ◽  
Navigation System ◽  
Near Field ◽  
Low Frequency ◽  
Greenland Ice Sheet ◽  
Radio Waves ◽  
Glacial Ice ◽  
Very Low Frequency ◽  
Ice Cap ◽  
The Earth

1. INTRODUCTION. Very-low-frequency radio waves were used to implement the Omega navigation system because of their low attenuation (2–4 dB/1000 km) when propagating globally in the waveguide formed between the Earth and the ionosphere. However, it became apparent in the early seventies, throughout the period when the majority of the stations of the Omega network were commissioned, that VLF signals propagating over permafrost or glacial ice could suffer anomalously large attenuations, of greater than 20 dB/1000 km, especially during the daytime. In the Northern Hemisphere problems have arisen with the heavy attenuation of Omega signals propagating over the Greenland ice sheet. In particular a very bad region for Omega coverage occurs around Winnipeg in Canada (the ‘Winnipeg Hole’). In this area Omega North Dakota suffers from ‘near field’ effects, Omega Liberia is contaminated by trans-equatorial modal effects and Omega Norway is removed by the attenuation of its signals when crossing the Greenland ice-cap. There have even been discussions on the feasibility of constructing extra VLF transmitters in Canada to alleviate this problem.

UNIPOLE METHOD OF ELECTRICAL PROFILING

Geophysics ◽  
1963 ◽  
Vol 28 (4) ◽  
pp. 608-616 ◽  
Author(s):  
Ravindra N. Gupta ◽  
P. K. Bhattacharya
Keyword(s):  
Field Measurements ◽  
Experimental Comparison ◽  
Response Curves ◽  
Resistive Layer ◽  
Near Surface ◽  
The Earth ◽  
Common Electrode ◽  
The Difference ◽  
General Response ◽  
Depth Of Investigation

In the unipole method of resistivity prospecting, an electrode arrangement AMNA′ with a third common electrode at infinity, is used as against the arrangement AMNB in the conventional bipole method. The electrodes A and A′ are connected to one and the same pole of electric current. In the case of the unipole method, field intensity at the center of the spread is zero for a homogeneous ground. This results in a pure‐anomaly method, increasing the depth of investigation and the sensitivity of field measurements considerably. The percentage of total current entering the deeper regions is larger in the unipole method than in the bipole method. The difference is further increased if a less resistive layer is present near the surface of the earth. Sensitivity of the unipole method to the near‐surface inhomogeneities is less than that of the bipole method. But the unipole method is more sensitive to the deeper inhomogeneities of interest. The unipole arrangement introduces some focusing of the current within a particular range of the depth which can be controlled by altering the spacing between the current electrodes. In general, response curves for the unipole method are less complicated and admit more controls for interpretation than those for the bipole method. A theoretical and experimental comparison of the unipole method with the conventional bipole method shows that the former method is more effective than the latter in certain applications. The field instruments used at present for the bipolar measurements can be very easily adapted to the unipole method.

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