scholarly journals The structure of strongly tilted current sheets in the Earth magnetotail

2014 ◽  
Vol 32 (2) ◽  
pp. 133-146 ◽  
Author(s):  
I. Y. Vasko ◽  
A. V. Artemyev ◽  
A. A. Petrukovich ◽  
R. Nakamura ◽  
L. M. Zelenyi
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Current Density ◽  
Neutral Plane ◽  
Current Sheets ◽  
Transverse Current ◽  
The Earth ◽  
Electron Current Density ◽  
Total Current Density ◽  
Using Data

Abstract. We investigate strongly tilted (in the y–z GSM plane) current sheets (CSs) in the Earth magnetotail using data from the Cluster mission. We analyze 29 CS crossings observed in 2001–2004. The characteristic current density, magnetic field at the CS boundary and the CS thickness of strongly tilted CSs are similar to those reported previously for horizontal (not tilted) CSs. We confirm that strongly tilted CSs are generally characterized by a rather large northward component of the magnetic field. The field-aligned current in strongly tilted CSs is on average two times larger than the transverse current. The proton adiabaticity parameter, κp, is larger than 0.5 in 85% of strongly tilted CSs due to the large northward magnetic field. Thus, the proton dynamics is stochastic for 18 current sheets with 0.5 < κp < 3 and protons are magnetized for 6 sheets with κp > 3, whereas electrons are magnetized for all observed current sheets. Strongly tilted CSs provide a unique opportunity to measure the electric field component perpendicular to the CS plane. We find that most of the electric field perpendicular to the CS plane is due to the decoupling of electron and ion motions (plasma polarization). For 27 CSs we determine profiles of the electrostatic potential, which is due to the plasma polarization. Drops in the potential between the neutral plane and the CS boundary are within the range of 200 V to 12 kV, while maximal values of the electric field are within the range of 0.2 mV m−1 to 8 mV m−1. For 16 CSs the observed potentials are in accordance with Ohm's law, if the electron current density is assumed to be comparable to the total current density. In 15 of these CSs the profile of the polarization potential is approximately symmetric with respect to the neutral plane and has minimum therein.

Estimation of Local Current Transport Properties in Thin Film Superconductor Based on Scanning Hall-probe Microscopy

2012 ◽  
Vol 1434 ◽  
Author(s):  
Kohei Higashikawa ◽  
Kei Shiohara ◽  
Masayoshi Inoue ◽  
Takanobu Kiss ◽  
Masateru Yoshizumi ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Thin Film ◽  
Critical Current Density ◽  
Electric Field ◽  
Critical Current ◽  
Current Density ◽  
Limiting Factors ◽  
Hall Probe ◽  
Scanning Hall Probe Microscopy ◽  
Field Criterion

ABSTRACTTo enhance a global critical current in a superconductor, it is indispensable to understand current limiting factors and their influence on such a critical current. From this point of view, we have investigated in-plane distribution of local critical current density and its electric field criterion in a thin-film superconductor by using scanning-Hall probe microscopy. In a remanent state, after the application of sufficiently high magnetic field to a sample, current flows at critical current density according to the critical state model. Such distribution of current density was estimated from that of measured magnetic field using the Biot-Savart law. Furthermore, the corresponding electric field criterion was evaluated from the relaxation of such remanent magnetic field by considering Faraday’s law. This means that we could estimate in-plane distribution of local critical current density as a function of electric field criterion in a nondestructive manner. This characterization method would be very helpful for finding current limiting factors in a thin-film superconductor and their influence on its global current density versus electric field properties which would usually be obtained by four-probe method.

scholarly journals An experimental examination of the electrostatic behaviour of supraconductors.

1936 ◽  
Vol 155 (884) ◽  
pp. 102-110 ◽  
Author(s):  
Heinz London ◽  
Frederick Alexander Lindemann
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Electric Field ◽  
Magnetic Field Strength ◽  
Current Density ◽  
Experimental Examination ◽  
Characteristic Constant

In previous papers of F. and H. London supraconductivity has been described as a phenomenon, in which the current density is not connected with the electric field, as in normal conductors, but depends on magnetic field strength according to the equation Λ c curl J = - H with B = H and with Λ = m / ne 2, a new characteristic constant which contains the number n of supraconducting electrons. the behaviour of the electric field is not completely determined by this equation. Using Maxwell's induction law one can conclude from (1) only that Λ c curl j = c curl E or Λj = E + grand μ, where the physical signifance of grad μ is yet unknown.

Variations of electrical characteristics of near-surface atmosphere of the Earth during magnetic storm

2020 ◽  
Author(s):  
Svetlana Riabova ◽  
Alexander Spivak
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Magnetic Storms ◽  
Electrical Characteristics ◽  
Near Surface ◽  
Russian Academy Of Sciences ◽  
The Earth ◽  
Geosphere Dynamics ◽  
Academy Of Sciences ◽  
The Magnetic Field

&lt;p&gt;Temporal variations of the electric field in near-surface layer of the Earth are determined by many factors, among which strong disturbances of the magnetic field should be especially noted. Magnetic storms cause an increase in the ionospheric electric field, which leads to variations in the gradient of the electric field potential near the Earth's surface. We consider the effect of magnetic storms in variations in the electrical characteristics of the atmosphere at Geophysical observatory &amp;#171;Mikhnevo&amp;#187; of Sadovsky Institute of Geosphere Dynamics of Russian Academy of Sciences and at Center for geophysical monitoring of Moscow of Sadovsky Institute of Geosphere Dynamics of Russian Academy of Sciences. We used data from the continuous monitoring of three components of the magnetic field, vertical components of the atmospheric electric field and atmospheric current carried out in fair weather. Experimental data processing and analysis show that accompanying magnetic storms with geomagnetic K index more or equal 5 increased variations in the electric field and vertical atmospheric current are characterized by different morphological structures. It is currently difficult to interpret the data. Nevertheless, the research results can be of great help in the development and verification of theoretical and computational models for generating variations in the electric field as a result of strong geomagnetic disturbances.&lt;/p&gt;

A robust integral equation solution for electromagnetic scattering by a thin plate in conductive media

Geophysics ◽  
1991 ◽  
Vol 56 (8) ◽  
pp. 1140-1152 ◽  
Author(s):  
P. W. Walker ◽  
G. F. West
Keyword(s):  
Magnetic Field ◽  
Integral Equation ◽  
Electric Field ◽  
Thin Plate ◽  
Current Density ◽  
Scalar Potential ◽  
The Other ◽  
Em Scattering ◽  
Equation Solution ◽  
Host Medium

An integral equation solution for electromagnetic (EM) scattering by a thin plate robustly models scattering in either perfectly resistive, very resistive, or conducting host media. Because the solution is not restricted to modeling certain ranges of host conductivity, it can be used to model scattering over the large ranges in conductivity encountered in geophysics. The solution is developed around a pair of coupled integral equations for the scattering distributions on the plate. In one equation, the scattering distribution is the scalar potential set up by the scattered charge distribution. In the other, it is the component of the scattered magnetic field perpendicular to the plate. The equations are solved numerically using the Galerkin method with simple polynomial basis functions. To find the fields scattered by the conductor, the scattered current density is first calculated from the scalar potential and the magnetic field. The scattered fields can then be found by integrating over the scattered current density. To test the solution, we model horizontal loop EM responses with our solution and compare the results with those from two established integral equation solutions. One of these solutions models pure induction and is used to test our solution when the host is perfectly resistive. Agreement with this solution is very good. Comparisons with the other solution, an electric field integral equation, tests our solution when the host medium is conductive. Agreement with the latter solution is good where induction is not too strong: i.e., where the electric‐field solution is known to work well. Our solution therefore can accurately model EM scattering by a plate in a host medium with any conductivity.

NONLINEAR CURRENT DENSITY IN QUANTUM WELLS WITH PARABOLIC POTENTIAL UNDER CROSSED ELECTRIC AND MAGNETIC FIELDS

2012 ◽  
Vol 01 (02) ◽  
pp. 1250021
Author(s):  
BUI DINH HOI ◽  
TRAN CONG PHONG
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Electric Field ◽  
Quantum Wells ◽  
Effective Mass ◽  
Current Density ◽  
Electrical Transport ◽  
Physical Parameters ◽  
Electric And Magnetic Fields ◽  
Dc Electric Field

The DC electrical transport in a quantum well (QW) with parabolic confinement potential [Formula: see text] (where m and ωz are the effective mass of electron and the confinement frequency in z direction, respectively) subjected to a crossed DC electric field and magnetic field, is studied theoretically. The scattering by optical phonons is taken into account at high temperatures and strong magnetic fields. We obtained the expression for nonlinear current density (NCD) involving external (electric and magnetic) fields and characteristic parameters of QW. The dependence of NCD on the DC electric field is complicated. The analytical result is computationally evaluated and graphically plotted for a specific parabolic QW of GaAs / AlGaAs . The numerical results show the appearance of maximum peaks satisfying the condition of intersubband magnetophonon resonance (MPR) effect in the presence of a DC electric field. Especially, we show that the effect can be applied in experiment to determine some physical parameters by using magnetic field, such as the numbers of Landau levels for which electrons transfer, the effective mass, the charge of electrons or the confinement frequency characterized for PQW.

scholarly journals Effect of Electromagnetic Field (EMF) and Electric Field (EF) on Some Behavior of Honeybees (Apis melliferaL.)

2019 ◽  
Author(s):  
Yaşar Erdoğan ◽  
Mahir Murat Cengiz
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Helmholtz Coils ◽  
Electro Magnetic Field ◽  
Sugar Syrup ◽  
The Earth ◽  
Rapid Spread ◽  
Electrical Devices ◽  
Electro Magnetic ◽  
The Magnetic Field

ABSTRACTGeomagnetic field can be used by different magnetoreception mechanisms, for navigation and orientation by honeybees. The present study analyzed the effects of magnetic field on honeybees. This study was carried out in 2017 at the Bayburt University Beekeeping Application Station. In this study, the effect of Electro Magnetic field (EMF) and electric field (EF) on the time of finding the source of food of honeybees and the time of staying there were determined. The honeybees behaviors were analyzed in the presence of external magnetic fields generated by Helmholtz coils equipment. The Electro Magnetic field values of the coils were fixed to 0 μT (90mV/m), 50 μT (118 mV/m), 100 μT (151 mV/m), 150 μT (211 mV/m), 200 μT (264 mV/m). Petri dishes filled with sugar syrup were placed in the center of the coils. According to the study, honeybees visited at most U1 (mean =21.0±17.89 bees) and at least U5 (mean =10.82±11.77 bees). Honeybees waited for the longest time in U1 (mean =35.27±6.97 seconds) and at least in U5 (mean =12.28±5.58 seconds). According to the results obtained from this first study showed that honeybees are highly affected by electromagnetic radiation and electric field.SummaryHoneybees uses the magnetic field of the earth to to determine their direction. Nowadays, the rapid spread of electrical devices and mobile towers leads to an increase in man-made EMF. This causes honeybees to lose their orientation and thus lose their hives.

Thin current sheets of sub-ion scales observed in planetary magnetotails

2021 ◽  
Author(s):  
Elena Grigorenko ◽  
Makar Leonenko ◽  
Lev Zelenyi ◽  
Helmi Malova ◽  
Victor Popov
Keyword(s):  
Magnetic Field ◽  
Larmor Radius ◽  
High Time Resolution ◽  
Current Layer ◽  
Ion Composition ◽  
Kinetic Description ◽  
Small Component ◽  
Current Sheets ◽  
The Earth ◽  
Plasma Characteristics

&lt;p&gt;Current sheets (CSs) play a crucial role in the storage and conversion of magnetic energy in planetary magnetotails. Spacecraft observations in the terrestrial magnetotail reported that the CS thinning and intensification can result in formation of multiscale current structure in which a very thin and intense current layer at the center of the CS is embedded into a thicker sheet. To describe such CSs fully kinetic description taking into account all peculiarities of non-adiabatic particle dynamics is required. Kinetic description brings kinetic scales to the CS models. Ion scales are controlled by thermal ion Larmor radius, while scales of sub-ion embedded CS are controlled by the topology of magnetic field lines until the electron motion is magnetized by a small component of the magnetic field existing in a very center of the CS. MMS observations in the Earth magnetotail as well as MAVEN observations in the Martian magnetotail with high time resolution revealed the formation of similar multiscale structure of the cross-tail CS in spite of very different local plasma characteristics. We revealed that the typical half&amp;#8208;thickness of the embedded Super Thin Current Sheet (STCSs) observed at the center of the CS in the magnetotails of both planets is much less than the gyroradius of thermal protons. The formation of STCS does not depend on ion composition, density and temperature, &amp;#160;but it is controlled by the small value of the normal component of the magnetic &amp;#64257;eld at the neutral plane. Our analysis showed that there is a good agreement between the spatial scaling of multiscale CSs observed in both magnetotails and the scaling predicted by the quasi-adiabatic model of thin anisotropic CS taking into account the coupling between ion and electron currents. Thus, in spite of the signi&amp;#64257;cant differences in the CS formation, ion composition, and plasma characteristics in the Earth&amp;#8217;s and Martian magnetotails, similar kinetic features are observed in the CS structures in the magnetotails of both planets. This phenomenon can be explained by the universal principles of nature. The CS once has been formed, then it should be self-consistently supported by the internal coupling of the total current carried by particles in the CS and its magnetic con&amp;#64257;guration, and as soon as the system achieved the quasi-equilibrium state, it &amp;#8220;forgets&amp;#8221; the mechanisms of its formation, and its following existence is ruled by the general principles of plasma kinetic described by Vlasov&amp;#8211;Maxwell equations.&lt;/p&gt;&lt;p&gt;This work is supported by the Russian Science Foundation grant &amp;#8470; 20-42-04418&lt;/p&gt;

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