Extracting geoelectrical maps from vintage very-low-frequency airborne data, tipper inversion, and interpretation: A case study from northern Sweden

Geophysics ◽  
2016 ◽  
Vol 81 (5) ◽  
pp. B135-B147 ◽  
Author(s):  
Sayyed Mohammad Abtahi ◽  
Laust Börsting Pedersen ◽  
Jochen Kamm ◽  
Thomas Kalscheuer
Keyword(s):  
Magnetic Field ◽  
Apparent Resistivity ◽  
Vertical Component ◽  
Low Frequency ◽  
High Resistivity ◽  
Clear Correlation ◽  
Northern Sweden ◽  
Very Low Frequency ◽  
Basaltic Composition ◽  
The Magnetic Field

In 1985, the mining company Luossavaara-Kiirunavaara Aktiebolag collected airborne very-low-frequency (VLF) data in northern Sweden. The operators stored only the vertical component and the total magnetic field, which at that time were believed to be sufficient for qualitative interpretation. Therefore, the data could not be directly used for quantitative tensor VLF processing and inversion. To avoid the costs of resurveying, we have developed a novel technique to estimate the tippers from the measured VLF data by computing anomalous and normal parts of the horizontal components of the magnetic field from two transmitters separately. Retrieval of the normal horizontal components was possible because one component of the horizontal magnetic field was used as the phase reference during the measurements. Additionally, we have determined how the approximate apparent resistivity suitable for data visualization can be computed from the components of the magnetic field assuming an average normal resistivity of the subsurface. Maps of apparent resistivity combined with topography show a clear correlation between high topography and high resistivity, whereas conductive zones are found in valleys in between. More importantly, the 3D model inverted from the calculated tippers shows excellent agreement with a map of the surface geology. Based on this comparison, some less resistive zones can be related to fluids in fractures and others can be related to mineralized contact zones. We suggest to focus further exploration on conductive zones surrounding areas with basaltic composition.

scholarly journals Electromagnetic image of small UAV in very low frequency range

2018 ◽  
Vol 69 (6) ◽  
pp. 438-441 ◽  
Author(s):  
Josef Blažek ◽  
Pavol Lipovský ◽  
František Heško ◽  
Dušan Repčík
Keyword(s):  
Magnetic Field ◽  
Low Frequency ◽  
Signal Spectrum ◽  
3D Analysis ◽  
Very Low Frequency ◽  
3D Space ◽  
Flight Mode ◽  
Frequency Components ◽  
Recorded Data ◽  
The Magnetic Field

Abstract The article deals with the measurement, visualization and analysis of the magnetic field in the 3D space around a small quadcopter. The measurements were realized in the very low frequency (VLF) range, since this range is interesting because of the possible detection of the drone also in the fully automated flight mode (without telemetry transmission). A measurement equipment/device that allows mapping of the magnetic field of the multirotor drone based on the sensor elevation and the copters azimuth was realized. The magnetic field was measured with a small inductive sensor – the air coil. Frequency analysis (signal spectrum) and the spatial 3D analysis of the selected frequency components that brought interesting results were carried out on the recorded data.

THE INFLUENCE OF THE IONOSPHERE ON THE VERTICAL FORCE EXCITED BY A HORIZONTAL ELECTRIC DIPOLE

2020 ◽  
pp. 68-76
Author(s):  
P. E. Tereshchenko
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Vertical Component ◽  
Low Frequency ◽  
Vertical Force ◽  
Frequency Range ◽  
The Earth ◽  
Horizontal Electric Dipole ◽  
Lower Frequency Range ◽  
The Magnetic Field

An analytical expression for the vertical component of the magnetic field has been obtained, with the help of which calculations have been made showing the effect of the ionosphere on the low-frequency field in the Earth-ionosphere waveguide. At distances from the source that are less than the doubled waveguide height, in ELF, and a lower frequency range, noticeable changes in the field strength caused by the state of the ionosphere are found.

scholarly journals Numerical simulation of the ground distribution of the field strength of an on-board low-frequency transmitter located in the ionosphere.

2021 ◽  
Author(s):  
A.V. Moshkov ◽  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Geomagnetic Latitude ◽  
Vertical Component ◽  
Low Frequency ◽  
Lower Ionosphere ◽  
Loop Current ◽  
The Earth ◽  
Transmitting Antenna ◽  
The Magnetic Field

Projects of active experiments in the ionosphere and the magnetosphere of the Earth and planets often include powerful low-frequency transmitters installed on-board of a spacecraft. Such sources are very effective, but their radiation is extremely heterogeneous in space because of the anisotropy of the ionospheric plasma due to the presence of the magnetic field of the Earth. This paper is devoted to numerical modeling of a distribution of the wave field strength near the Earth surface. The work examines a specific active wave experiment with a 20 m loop as a transmitting antenna. The satellite is assumed to orbit with an inclination of 82.5 degrees at an average altitude of 1000 km. All calculations are performed in linear approximation using the cold magneto-active plasma model. The computation model uses ray approximation everywhere except for the highly heterogeneous lower ionosphere, where a full wave equations set is applied. It is shown that the maximum magnetic field value is decreased with increasing of the geomagnetic latitude value and the strength range is 1… 2 nA/m for frequency 10 kHz and loop current 100 A. The magnitude of the vertical component of the electric field lies in the range of 0.4 ... 0.8 μV/m. An average Doppler frequency shift is equal to ~0.4 Hz. A comparison is made between the data of the numerical experiment and the results of simple estimations of the values of the magnetic field strength at the maximum of the ground distribution.

PEMANFAATAN RADIASI ENERGI TEGANGAN 150 KV UNTUK LAMPU LED PENERANGAN JALAN

Jurnal Teknik ◽  
2018 ◽  
Vol 7 (1) ◽  
Author(s):  
Mauludi Manfaluthy
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
High Voltage ◽  
Low Frequency ◽  
Energy Utilization ◽  
World Health ◽  
Electromagnetic Signals ◽  
Health Organization ◽  
The Magnetic Field ◽  
Low Frequency Waves

WHO (World Health Organization) concludes that not much effect is caused by electric field up to 20 kV / m in humans. WHO standard also mentions that humans will not be affected by the magnetic field under  100 micro tesla and that the electric field will affect the human body with a maximum standard of 5,000 volts per meter. In this study did not discuss about the effect of high voltage radiation SUTT (High Voltage Air Channel) with human health. The research will focus on energy utilization of SUTT radiation. The combination of electric field and magnetic field on SUTT (70-150KV) can generate electromagnetic (EM) and radiation waves, which are expected to be converted to turn on street lights around the location of high voltage areas or into other forms. The design of this prototype works like an antenna in general that captures electromagnetic signals and converts them into AC waves. With a capacitor that can store the potential energy of AC and Schottky diode waves created specifically for low frequency waves, make the current into one direction (DC). From the research results obtained the current generated from the radiation is very small even though the voltage is big enough.Keywords : Radiance Energy, Joule Thief, and  LED Module.

scholarly journals Integral Equations for Problems on Wave Propagation in Near-Earth Plasma

Symmetry ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1395
Author(s):  
Danila Kostarev ◽  
Dmitri Klimushkin ◽  
Pavel Mager
Keyword(s):  
Magnetic Field ◽  
Integral Equations ◽  
Field Potential ◽  
Low Frequency ◽  
Fredholm Equation ◽  
Compression Waves ◽  
Parallel Component ◽  
Electric Field Potential ◽  
The Magnetic Field ◽  
Low Frequency Waves

We consider the solutions of two integrodifferential equations in this work. These equations describe the ultra-low frequency waves in the dipol-like model of the magnetosphere in the gyrokinetic framework. The first one is reduced to the homogeneous, second kind Fredholm equation. This equation describes the structure of the parallel component of the magnetic field of drift-compression waves along the Earth’s magnetic field. The second equation is reduced to the inhomogeneous, second kind Fredholm equation. This equation describes the field-aligned structure of the parallel electric field potential of Alfvén waves. Both integral equations are solved numerically.

scholarly journals Properties of the inner penumbral boundary and temporal evolution of a decaying sunspot

2018 ◽  
Vol 620 ◽  
pp. A191 ◽  
Author(s):  
M. Benko ◽  
S. J. González Manrique ◽  
H. Balthasar ◽  
P. Gömöry ◽  
C. Kuckein ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Flux ◽  
Temporal Evolution ◽  
Vertical Component ◽  
Field Vector ◽  
Linear Increase ◽  
Vertical Magnetic Field ◽  
Magnetic Diffusion ◽  
The Magnetic Field ◽  
Linear Decay

Context. It has been empirically determined that the umbra-penumbra boundaries of stable sunspots are characterized by a constant value of the vertical magnetic field. Aims. We analyzed the evolution of the photospheric magnetic field properties of a decaying sunspot belonging to NOAA 11277 between August 28–September 3, 2011. The observations were acquired with the spectropolarimeter on-board of the Hinode satellite. We aim to prove the validity of the constant vertical magnetic-field boundary between the umbra and penumbra in decaying sunspots. Methods. A spectral-line inversion technique was used to infer the magnetic field vector from the full-Stokes profiles. In total, eight maps were inverted and the variation of the magnetic properties in time were quantified using linear or quadratic fits. Results. We find a linear decay of the umbral vertical magnetic field, magnetic flux, and area. The penumbra showed a linear increase of the vertical magnetic field and a sharp decay of the magnetic flux. In addition, the penumbral area quadratically decayed. The vertical component of the magnetic field is weaker on the umbra-penumbra boundary of the studied decaying sunspot compared to stable sunspots. Its value seem to be steadily decreasing during the decay phase. Moreover, at any time of the sunspot decay shown, the inner penumbra boundary does not match with a constant value of the vertical magnetic field, contrary to what is seen in stable sunspots. Conclusions. During the decaying phase of the studied sunspot, the umbra does not have a sufficiently strong vertical component of the magnetic field and is thus unstable and prone to be disintegrated by convection or magnetic diffusion. No constant value of the vertical magnetic field is found for the inner penumbral boundary.

scholarly journals Spacecraft and interplanetary contributions to the magnetic environment on-board LISA Pathfinder

2020 ◽  
Vol 494 (2) ◽  
pp. 3014-3027
Author(s):  
M Armano ◽  
H Audley ◽  
J Baird ◽  
P Binetruy ◽  
M Born ◽  
...  
Keyword(s):  
Magnetic Field ◽  
New Technologies ◽  
Magnetic Measurements ◽  
Magnetic Measurement ◽  
Low Frequency ◽  
Lisa Pathfinder ◽  
Frequency Regime ◽  
The Magnetic Field ◽  
Instrument Sensitivity ◽  
Stationary Component

ABSTRACT LISA Pathfinder (LPF) has been a space-based mission designed to test new technologies that will be required for a gravitational wave observatory in space. Magnetically driven forces play a key role in the instrument sensitivity in the low-frequency regime (mHz and below), the measurement band of interest for a space-based observatory. The magnetic field can couple to the magnetic susceptibility and remanent magnetic moment from the test masses and disturb them from their geodesic movement. LPF carried on-board a dedicated magnetic measurement subsystem with noise levels of 10 $\rm nT \ Hz^{-1/2}$ from 1 Hz down to 1 mHz. In this paper we report on the magnetic measurements throughout LPF operations. We characterize the magnetic environment within the spacecraft, study the time evolution of the magnetic field and its stability down to 20 μHz, where we measure values around 200 $\rm nT \ Hz^{-1/2}$, and identify two different frequency regimes, one related to the interplanetary magnetic field and the other to the magnetic field originating inside the spacecraft. Finally, we characterize the non-stationary component of the fluctuations of the magnetic field below the mHz and relate them to the dynamics of the solar wind.

scholarly journals ANALYSIS OF HIGH-FREQUENCY C-CORE MAGNETIC FLUX LEAKAGES FOR BONE TUMOR WITH INDUCTION HEATING BY USING MULTI-COIL

2019 ◽  
Author(s):  
Metharak Jokpudsa ◽  
Supawat Kotchapradit ◽  
Chanchai Thongsopa ◽  
Thanaset Thosdeekoraphat
Keyword(s):  
Magnetic Field ◽  
High Frequency ◽  
Tumor Tissue ◽  
Low Frequency ◽  
Heat Energy ◽  
High Frequencies ◽  
Frequency Magnetic Field ◽  
High Frequency Magnetic Field ◽  
The Magnetic Field ◽  
Flux Leakage

High-frequency magnetic field has been developed pervasively. The induction of heat from the magnetic field can help to treat tumor tissue to a certain extent. Normally, treatment by the low-frequency magnetic field needed to be combined with magnetic substances. To assist in the induction of magnetic fields and reduce flux leakage. However, there are studies that have found that high frequencies can cause heat to tumor tissue. In this paper present, a new magnetic application will focus on the analysis of the high-frequency magnetic nickel core with multi-coil. In order to focus the heat energy using a high-frequency magnetic field into the tumor tissue. The magnetic coil was excited by 915 MHz signal and the combination of tissues used are muscle, bone, and tumor. The magnetic power on the heating predicted by the analytical model, the power loss density (2.98e-6 w/m3) was analyzed using the CST microwave studio.

scholarly journals Beach sands deposite identification using very low frequency method in the Benteng Lubuk, Krueng Raya coastal area

2021 ◽  
Vol 869 (1) ◽  
pp. 012058
Author(s):  
M Jannah ◽  
M Muhammad ◽  
Marwan ◽  
Z Jalil
Keyword(s):  
Sea Water ◽  
Low Frequency ◽  
High Resistivity ◽  
Conductive Layer ◽  
Inversion Process ◽  
Frequency Method ◽  
Sea Water Intrusion ◽  
Resistive Layer ◽  
Very Low Frequency ◽  
Beach Sands

Abstract The 2D subsurface identification work of iron sands in Benteng Lubuk, Krueng Raya was successfully studied using the very low frequency method based on resistivity mode (VLF-R). This study aims to identify iron sand deposits in coastal areas using electromagnetic inversion. The inversion process shows a conductivity zone of iron sand area, where the resistive layer is strongly covered by a conductive layer above it. High resistivity values were found at 80-100 m stations. This layer has a resistivity value between 20000 – 40000 m and the conductivity value tend to be low. It is estimated that at this point there will only be manifestations of iron sand or sea water intrusion, due to the location of the track close to the coastline.

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