scholarly journals Effect of Ergodic and Non-Ergodic Fluctuations on a Charge Diffusing in a Stochastic Magnetic Field

Entropy ◽  
2021 ◽  
Vol 23 (6) ◽  
pp. 781
Author(s):  
Gerardo Aquino ◽  
Kristopher J. Chandía ◽  
Mauro Bologna
Keyword(s):  
Magnetic Field ◽  
Basic Problem ◽  
Waiting Time Distribution ◽  
Field Fluctuations ◽  
Ergodic Fluctuations ◽  
A Charge ◽  
Ergodicity Breaking ◽  
Mean Time ◽  
Stochastic Magnetic Field ◽  
The Magnetic Field

In this paper, we study the basic problem of a charged particle in a stochastic magnetic field. We consider dichotomous fluctuations of the magnetic field where the sojourn time in one of the two states are distributed according to a given waiting-time distribution either with Poisson or non-Poisson statistics, including as well the case of distributions with diverging mean time between changes of the field, corresponding to an ergodicity breaking condition. We provide analytical and numerical results for all cases evaluating the average and the second moment of the position and velocity of the particle. We show that the field fluctuations induce diffusion of the charge with either normal or anomalous properties, depending on the statistics of the fluctuations, with distinct regimes from those observed, e.g., in standard Continuous-Time Random Walk models.

scholarly journals Multi-point observations of intermittency in the cusp regions

2007 ◽  
Vol 14 (4) ◽  
pp. 525-534 ◽  
Author(s):  
M. M. Echim ◽  
H. Lamy ◽  
T. Chang
Keyword(s):  
Magnetic Field ◽  
Magnetic Energy ◽  
Haar Wavelet ◽  
Distribution Functions ◽  
Statistical Properties ◽  
Coarse Grained ◽  
Haar Wavelet Transform ◽  
Intermittent Behavior ◽  
Field Fluctuations ◽  
The Magnetic Field

Abstract. In this paper we investigate the statistical properties of magnetic field fluctuations measured by the four Cluster spacecraft in the cusp and close to the interface with the magnetospheric lobes, magnetopause and magnetosheath. At lower altitudes along the outbound orbit of 26 February 2001, the magnetic field fluctuations recorded by all four spacecraft are random and their Probability Distribution Functions (PDFs) are Gaussian at all scales. The flatness parameter, F – related to the kurtosis of the time series, is equal to 3. At higher altitudes, in the cusp and its vicinity, closer to the interface with the magnetopause and magnetosheath, the PDFs from all Cluster satellites are non-Gaussian and show a clear intermittent behavior at scales smaller than τG≈ 61 s (or 170 km). The flatness parameter increases to values greater than 3 for scales smaller than τG. A Haar wavelet transform enables the identification of the "events" that produce sudden variations of the magnetic field and of the scales that have most of the power. The LIM parameter (i.e. normalized wavelet power) indicates that events for scales below 65 s are non-uniformly distributed throughout the cusp passage. PDFs, flatness and wavelet analysis show that at coarse-grained scales larger than τG the intermittency is absent in the cusp. Fluctuations of the magnetic energy observed during the same orbit in the magnetosheath show PDFs that tend toward a Gaussian at scales smaller than τG found in the cusp. The flatness analysis confirms the decreasing of τG from cusp to magnetosheath. Our analysis reveals the turbulent cusp as a transition region from a non-intermittent turbulent state inside the magnetosphere to an intermittent turbulent state in the magnetosheath that has statistical properties resembling the solar wind turbulence. The observed turbulent fluctuations in the cusp suggests a phenomenon of nonlinear interactions of plasma coherent structures as in contemporary models of space plasma turbulence.

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

MAGNETORESISTANCE IN COPPER

2008 ◽  
Vol 22 (25n26) ◽  
pp. 4434-4441
Author(s):  
SHIGEJI FUJITA ◽  
NEBI DEMEZ ◽  
JEONG-HYUK KIM ◽  
H. C. HO
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Kinetic Theory ◽  
Anisotropic Magnetoresistance ◽  
Magnetic Field Direction ◽  
Conduction Electrons ◽  
Fcc Lattice ◽  
A Charge ◽  
The Magnetic Field ◽  
Cyclotron Mass

The motion of the guiding center of magnetic circulation generates a charge transport. By applying kinetic theory to the guiding center motion, an expression for the magnetoconductivity σ is obtained: σ = e2ncτ/M*, where M* is the magnetotransport mass distinct from the cyclotron mass, nc the density of the conduction electrons, and τ the relaxation time. The density nc depends on the magnetic field direction relative to copper's fcc lattice, when Cu's Fermi surface is nonspherical with “necks”. The anisotropic magnetoresistance is analyzed based on a one-parameter model, and compared with experiments. A good fit is obtained.

scholarly journals Propagation of an electromagnetic soliton in a ferromagnetic medium

2002 ◽  
Vol 44 (1) ◽  
pp. 103-110
Author(s):  
V. Veerakumar ◽  
M. Daniel
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Waves ◽  
Ferromagnetic Material ◽  
Linear Charge ◽  
Electromagnetic Soliton ◽  
Induction Components ◽  
Charged Medium ◽  
A Charge ◽  
The Magnetic Field ◽  
Ferromagnetic Medium

AbstractWe study the propagation of electromagnetic waves (EMWs) in both isotropic and anisotropic ferromagnetic material media. As the EMW propagates through linear charge-free isotropic and anisotropic ferromagnetic media, it is found that the magnetic field and the magnetic induction components of the EMW and the magnetization excitations of the medium are in the form of solitons. However, the electromagnetic soliton gets damped and decelerates in the case of a charged medium. In the case of a charge-free nonlinear ferromagnetic medium we obtain results similar to those for the linear case.

Waves in magnetoplasma with a stochastic magnetic field

1980 ◽  
Vol 23 (2) ◽  
pp. 311-320
Author(s):  
Y. S. Prahalad ◽  
M. L. Mittal
Keyword(s):  
Magnetic Field ◽  
Nonlinear Interaction ◽  
Linear Analysis ◽  
Coupling Coefficients ◽  
Transverse Waves ◽  
Circularly Polarized ◽  
Transverse Modes ◽  
Polarized Waves ◽  
Stochastic Magnetic Field ◽  
The Magnetic Field

In the present analysis, a normal mode approach is used to study waves in a plasma subjected to a spatially uniform but temporally stochastic magnetic field. The first part deals with the evolution of circularly polarized transverse waves. Making a linear analysis, it is shown that the coherent waves are damped. The nature of the damping is determined by the Kubo number. In the second part, the nonlinear interaction of three coherent waves propagating along the magnetic field is analyzed. The coupling coefficients for the interaction of two circularly polarized waves and a longitudinal one are calculated. It is shown that for coherent waves, the system is equivalent to the interaction of two damped transverse modes with an undamped longitudinal one.

Trapped particles around Jupiter detected by Advanced Stellar Compass

2020 ◽  
Author(s):  
Matija Herceg ◽  
John L. Jørgensen ◽  
Peter S. Jørgensen ◽  
Jose M. G. Merayo ◽  
Mathias Benn ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Pitch Angle ◽  
Magnetic Field Gradient ◽  
Rotation Period ◽  
High Energy ◽  
Radiation Shielding ◽  
Trapped Particles ◽  
Dipolar Fields ◽  
A Charge ◽  
The Magnetic Field

<p>The Advanced Stellar Compass (ASC), attitude reference for the MAG investigation onboard Juno, has continuously monitored high energy particles fluxes in Jupiter’s magnetosphere since Juno’s orbit insertion. The instrument performs this function by tracking the effects of radiation with sufficient energy to transit the instrument’s radiation shielding. Particles that Juno ASC observes have energy >15MeV for electrons, >80MeV for protons, and >~GeV for heavier elements.</p><p>Completing 24 highly elliptical orbits around Jupiter, results in a fairly detailed mapping of the trapped high energy flux at up to 20 Jupiter radius distances.</p><p>Traveling at velocities close to the speed of light, electrons measured by the ASC, maintain the motion governed by the three adiabatic invariants: gyrating motion around the magnetic field line, a north-south magnetic pole particle bounce, and a charge dependent drift around the planet.</p><p>The bounce period is much smaller than the Jovian rotation period, and a large east-west drift component is caused by the magnetic field gradient. For these reasons, the drift shell description traditionally used for dipolar fields, are far from adequate to describe the behavior of energetic particles travelling close to Jupiter.</p><p>In this work, we present the distribution of the trapped high energy electrons around Jupiter. Furthermore, we have constrained the spatial extent of the stable trapped regions and are presenting the distinctive pitch angle and its correlation with ”life” of a particle. At certain distances from Jupiter, pitch angle dependency is not as important to keep the particle trapped as is the injected energy. We also develop an adiabatic map which describes the radial bands for stable trapped particles as a function of the pitch angle and energy.</p><p> </p>

Multi-point observations of a reconnection outflow associated with interacting flux ropes in the solar wind

2020 ◽  
Author(s):  
Zoltan Vörös ◽  
Emiliya Yordanova ◽  
Owen Roberts ◽  
Yasuhito Narita
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Flow Shear ◽  
Magnetic Flux Ropes ◽  
Interplanetary Coronal Mass Ejection ◽  
Flux Ropes ◽  
Magnetic Field Magnitude ◽  
Field Fluctuations ◽  
Mass Ejection ◽  
The Magnetic Field

<p>Twisted magnetic flux ropes embedded in an interplanetary coronal mass ejection (ICME) often contain oppositely oriented magnetic fields and potentially reconnecting current sheets. Reconnection outflows in the solar wind can be identified through magnetic field and plasma signatures, for example, through decreasing magnetic field magnitude, enhanced bulk velocity, temperature and (anti)correlated rotations of the magnetic field and plasma velocity. We investigate a reconnection outflow observed by ACE, WIND and Geotail spacecraft within the interaction region of two flux ropes embedded into an ICME. The SOHO spacecraft, located 15 RE upstream, 120 RE in GSE Y and 5 RE in GSE Z direction from the ACE spacecraft, does not see any plasma signatures of the reconnection outflow. At the same time the other spacecraft, also separated by more than 200 RE in X and Y GSE directions, observe strong plasma and magnetic field fluctuations at the border of the exhaust.  The fluctuations could be associated with Kelvin-Helmholtz (KH) instability at the border of the reconnection outflow with strong flow shear.  It is speculated that the KH instability driven fluctuations and dissipation is responsible for stopping the reconnection outflow which is therefore not seen by SOHO.</p>

MAGNETORESISTANCE AND FIELD DEPENDENCE OF THE HALL EFFECT IN INDIUM ANTIMONIDE

1958 ◽  
Vol 36 (5) ◽  
pp. 527-538 ◽  
Author(s):  
Gaston Fischer ◽  
D. K. C. MacDonald
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Hall Effect ◽  
Field Dependence ◽  
Indium Antimonide ◽  
Charge Carriers ◽  
Band Theory ◽  
Hall Effect Measurements ◽  
A Charge ◽  
The Magnetic Field

Magnetoresistance and Hall-effect measurements in InSb are described. This semiconductor has charge carriers with sufficiently long mean free paths, l, that it is possible, even at room temperature and with available magnetic fields, to obtain l/r values considerably greater than unity, r being the orbital radius of a charge carrier moving in the applied magnetic field. The classical two-band theory has been found to account rather well for the results up to the highest magnetic fields employed. A review of the underlying assumptions of this theory is presented, and simple formulae are derived which allow the concentrations and mobilities of both types of carriers to be calculated from the magnetic field dependence of the resistivity, ρH, and of the Hall-constant, AH. The parameter Λ ≡ [(AH−A0)/A0]/[(ρH−ρ0)/ρ0] provides a useful means to check the consistency of the theory and can give some indication of the variation of the mobilities with the magnetic field.

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