scholarly journals An analytical expression for early electromagnetic signals generated by impulsive line-currents in conductive Earth crust, with numerical examples

2016 ◽  
Vol 59 (2) ◽  
Author(s):  
Ken'ichi Yamazaki
Keyword(s):  
Seismic Waves ◽  
Ground Surface ◽  
Space Model ◽  
Whole Space ◽  
Source Current ◽  
Em Field ◽  
Electromagnetic Signals ◽  
Analytical Expressions ◽  
The Magnetic Field ◽  
Ground Conductivity

<p>Changes in the electromagnetic (EM) field after an earthquake rupture but before the arrival of seismic waves (“early EM signals”) have sometimes been reported. Quantitative evaluations are necessary to clarify whether the observed phenomena are accounted for by known theories and to assess whether the phenomenon can be applied to earthquake early warning. Therefore, analytical expressions for the magnetic field generated by an impulsive line-current are derived for a conductive half-space model, and for a two-layer model; the somewhat simpler situation of a conductive whole-space is also considered. By analyzing the expressions obtained for the generated EM field, some expected features of the early EM signals are discussed. First, I verify that an early EM signal arrives before the seismic waves unless conductivity is relatively high. Second, I show that early EM signals are well approximated by the whole-space model when the source is near the ground surface, but not when it is at depth. Third, I show that the expected amplitudes of early EM signals are within the detection limits of commonly used EM sensors, provided that ground conductivity is not very high and that the source current is sufficiently intense. However, this does not mean that the EM signals are easily distinguishable, because detector sensitivity does not account for additive noise or false positive detections.</p>

scholarly journals Semi-analytical solutions of seismo-electromagnetic signals arising from the motional induction in 3-D multi-layered media: part II—numerical investigations

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Hengxin Ren ◽  
Ling Zeng ◽  
Yao-Chong Sun ◽  
Ken’ichi Yamazaki ◽  
Qinghua Huang ◽  
...  
Keyword(s):  
Point Source ◽  
Numerical Computation ◽  
Wave Velocity ◽  
Excellent Agreement ◽  
Seismic Waves ◽  
Averaging Method ◽  
Ground Surface ◽  
Induction Effect ◽  
Motional Induction ◽  
Electromagnetic Signals

AbstractIn this paper, numerical computations are carried out to investigate the seismo-electromagnetic signals arising from the motional induction effect due to an earthquake source embedded in 3-D multi-layered media. First, our numerical computation approach that combines discrete wavenumber method, peak-trough averaging method, and point source stacking method is introduced in detail. The peak-trough averaging method helps overcome the slow convergence problem, which occurs when the source–receiver depth difference is small, allowing us to consider any focus depth. The point source stacking method is used to deal with a finite fault. Later, an excellent agreement between our method and the curvilinear grid finite-difference method for the seismic wave solutions is found, which to a certain degree verifies the validity of our method. Thereafter, numerical computation results of an air–solid two-layer model show that both a receiver below and another one above the ground surface will record electromagnetic (EM) signals showing up at the same time as seismic waves, that is, the so-called coseismic EM signals. These results suggest that the in-air coseismic magnetic signals reported previously, which were recorded by induction coils hung on trees, can be explained by the motional induction effect or maybe other seismo-electromagnetic coupling mechanisms. Further investigations of wave-field snapshots and theoretical analysis suggest that the seismic-to-EM conversion caused by the motional induction effect will give birth to evanescent EM waves when seismic waves arrive at an interface with an incident angle greater than the critical angle θc = arcsin(Vsei/Vem), where Vsei and Vem are seismic wave velocity and EM wave velocity, respectively. The computed EM signals in air are found to have an excellent agreement with the theoretically predicted amplitude decay characteristic for a single frequency and single wavenumber. The evanescent EM waves originating from a subsurface interface of conductivity contrast will contribute to the coseismic EM signals. Thus, the conductivity at depth will affect the coseismic EM signals recorded nearby the ground surface. Finally, a fault rupture spreading to the ground surface, an unexamined case in previous numerical computations of seismo-electromagnetic signals, is considered. The computation results once again indicate the motional induction effect can contribute to the coseismic EM signals.

scholarly journals Estimating the seismotelluric current required for observable electromagnetic ground signals

2010 ◽  
Vol 28 (8) ◽  
pp. 1615-1624 ◽  
Author(s):  
J. Bortnik ◽  
T. E. Bleier ◽  
C. Dunson ◽  
F. Freund
Keyword(s):  
Simple Model ◽  
Current Source ◽  
Signal Power ◽  
Earthquake Hypocenter ◽  
Detectable Range ◽  
Source Current ◽  
Cardinal Directions ◽  
Electromagnetic Signals ◽  
Ground Conductivity ◽  
Detectability Threshold

Abstract. We use a relatively simple model of an underground current source co-located with the earthquake hypocenter to estimate the magnitude of the seismotelluric current required to produce observable ground signatures. The Alum Rock earthquake of 31 October 2007, is used as an archetype of a typical California earthquake, and the effects of varying the ground conductivity and length of the current element are examined. Results show that for an observed 30 nT pulse at 1 Hz, the expected seismotelluric current magnitudes fall in the range ~10–100 kA. By setting the detectability threshold to 1 pT, we show that even when large values of ground conductivity are assumed, magnetic signals are readily detectable within a range of 30 km from the epicenter. When typical values of ground conductivity are assumed, the minimum current required to produce an observable signal within a 30 km range was found to be ~1 kA, which is a surprisingly low value. Furthermore, we show that deep nulls in the signal power develop in the non-cardinal directions relative to the orientation of the source current, indicating that a magnetometer station located in those regions may not observe a signal even though it is well within the detectable range. This result underscores the importance of using a network of magnetometers when searching for preseismic electromagnetic signals.

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 Регистрация терагерцового излучения с помощью наноструктур карбида кремния

2021 ◽  
Vol 55 (12) ◽  
pp. 1195
Author(s):  
Н.Т. Баграев ◽  
С.А. Кукушкин ◽  
А.В. Осипов ◽  
Л.Е. Клячкин ◽  
A.М. Маляренко ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Incident Radiation ◽  
Thz Radiation ◽  
Device Structure ◽  
Paramagnetic Resonance ◽  
Kinetic Dependence ◽  
Proposed Model ◽  
Source Current ◽  
Electron Paramagnetic ◽  
The Magnetic Field

The response to external terahertz (THz) radiation from the silicon carbide nanostructures prepared by the method of substitution of atoms on silicon is investigated. The kinetic dependence of the longitudinal voltage is recorded at room temperature by varying the drain-source current in the device structure performed in a Hall geometry. In the frameworks of proposed model based on the quantum Faraday effect the incident radiation results in the appearance of a generated current in the edge channels with a change in the number of magnetic flux quanta and in the appearance of features in the kinetic dependence of the longitudinal voltage. The generation of intrinsic terahertz radiation inside the silicon carbide nanostructures is also revealed by the electrically-detected electron paramagnetic resonance (EDEPR) measured the longitudinal voltage as a function of the magnetic field value.

Analytical expressions for gravity anomalies due to homogeneous polyhedral bodies and translations into magnetic anomalies

Geophysics ◽  
1979 ◽  
Vol 44 (4) ◽  
pp. 730-741 ◽  
Author(s):  
M. Okabe
Keyword(s):  
Gravitational Potential ◽  
Computing Time ◽  
Gravity Anomalies ◽  
Magnetic Anomalies ◽  
Two Dimensions ◽  
First Derivative ◽  
Second Derivatives ◽  
Analytical Expressions ◽  
Derivatives Of ◽  
The Magnetic Field

Complete analytical expressions for the first and second derivatives of the gravitational potential in arbitrary directions due to a homogeneous polyhedral body composed of polygonal facets are developed, by applying the divergence theorem definitively. Not only finite but also infinite rectangular prisms then are treated. The gravity anomalies due to a uniform polygon are similarly described in two dimensions. The magnetic potential due to a uniformly magnetized body is directly derived from the first derivative of the gravitational potential in a given direction. The rule for translating the second derivative of the gravitational potential into the magnetic field component is also described. The necessary procedures for practical computer programming are discussed in detail, in order to avoid singularities and to save computing time.

Hierarchical simulated annealing vs. a Gauss‐Newton scheme applying analytical Jacobians for the solution of a source current distribution problem

2001 ◽  
Vol 20 (2) ◽  
pp. 497-506
Author(s):  
Bernhard Brandstätter ◽  
Christian Magele
Keyword(s):  
Simulated Annealing ◽  
Linear Problem ◽  
Computational Cost ◽  
Search Space ◽  
Quadratic Program ◽  
Source Current ◽  
Ill Posed ◽  
Newton Scheme ◽  
Future Work ◽  
The Magnetic Field

Considers, without loss of generality, a simple linear problem, where in a certain domain the magnetic field, generated by infinitely long conductors, whose locations as well as the currents are unknown, has to meet a certain figure. The problem is solved by applying hierarchical simulated annealing, which iteratively reduces the dimension of the search space to save computational cost. A Gauss‐Newton scheme, making use of analytical Jacobians, preceding a sequential quadratic program (SQP), will be applied as a second approach to tackle this severely ill‐posed problem. The results of these two techniques will be analyzed and discussed and some comments on future work will be given.

Covariant Electrodynamics in Vacuum

1990 ◽  
Vol 45 (5) ◽  
pp. 736-748
Author(s):  
H. E. Wilhelm
Keyword(s):  
Magnetic Field ◽  
Charged Particle ◽  
Relative Velocity ◽  
Light Propagation ◽  
Direction Parallel ◽  
Galilean Relativity ◽  
Ether Frame ◽  
Em Field ◽  
A Charge ◽  
The Magnetic Field

Abstract The generalized Galilei covariant Maxwell equations and their EM field transformations are applied to the vacuum electrodynamics of a charged particle moving with an arbitrary velocity v in an inertial frame with EM carrier (ether) of velocity w. In accordance with the Galilean relativity principle, all velocities have absolute meaning (relative to the ether frame with isotropic light propagation), and the relative velocity of two bodies is defined by the linear relation uG = v1 - v2. It is shown that the electric equipotential surfaces of a charged particle are compressed in the direction parallel to its relative velocity v - w (mechanism for physical length contraction of bodies). The magnetic field H(r, t) excited in the ether by a charge e moving uniformly with velocity v is related to its electric field E(r, t) by the equation H=ε0(v - w)xE/[ 1 +w • (t>- w)/c20], which shows that (i) a magnetic field is excited only if the charge moves relative to the ether, and (ii) the magnetic field is weak if v - w is not comparable to the velocity of light c0 . It is remarkable that a charged particle can excite EM shock waves in the ether if |i> - w\ > c0. This condition is realizable for anti-parallel charge and ether velocities if |v-w| > c0- | w|, i.e., even if |v| is subluminal. The possibility of this Cerenkov effect in the ether is discussed for terrestrial and galactic situations

Principles of probability tomography for natural‐source electromagnetic induction fields

Geophysics ◽  
1999 ◽  
Vol 64 (5) ◽  
pp. 1403-1417 ◽  
Author(s):  
Paolo Mauriello ◽  
Domenico Patella
Keyword(s):  
Electric Charge ◽  
Probability Function ◽  
Ground Surface ◽  
Magnetic Surface ◽  
Natural Source ◽  
Occurrence Probability ◽  
Suitable Parameter ◽  
Em Induction ◽  
Em Field ◽  
Induced Charge

The 3-D interpretation problem of natural‐source electromagnetic (EM) induction field data collected over a flat air‐earth boundary is dealt with using the concept of probability tomography. This paper presents a method to recognize the most probable localization of the induced electric charge accumulations across resistivity discontinuities and current channeling inside conductive bodies. We begin by writing the solutions for the electric (magnetic) ground surface EM field components in the frequency domain as a sum of elementary contributions, each resulting from a single induced‐charge (dipole) element. Then we express the total electric (magnetic) power associated with each EM field component as a sum of crosscorrelation integrals between the measured component and the homologous synthetic expression resulting from each causative induced‐charge (dipole) element. The synthetic component takes the key role of scanner function in the new imaging procedure. Moreover, using the crosscorrelation bounding inequality we introduce the concept of EM induction occurrence probability as a suitable parameter for the tomographic representation of the induced‐charge and dipole distributions underground. For each electric and magnetic surface component we define the corresponding occurrence probability function as the crosscorrelation product of the observed component and the relative scanning function, divided by the square root of the product of the respective variances. In the space domain, the 3-D tomographic procedure consists of scanning the half‐space below the survey area by the unit strength charge or dipole element, which is given a regular grid of space coordinates within the volume. At each node of the grid, the occurrence probability function is calculated. We use the complete set of calculated grid values to single out the zones of highest occurrence probability of electric charge accumulations and current channeling elements. The physical reliability of the proposed tomography is tested on synthetic and field examples.

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