Thermal fluctuations of the magnetic field over a thin conducting plate

1998 ◽  
Vol 83 (2) ◽  
pp. 635-638 ◽  
Author(s):  
Bradley J. Roth
Keyword(s):  
Magnetic Field ◽  
Thermal Fluctuations ◽  
Thin Conducting ◽  
Conducting Plate ◽  
The Magnetic Field

scholarly journals Alinement of Solid Interstellar Particles by a Magnetic Field

1965 ◽  
Vol 7 ◽  
pp. 73-76
Author(s):  
Lyman Spitzer ◽  
R. V. Jones
Keyword(s):  
Magnetic Field ◽  
Basic Mechanism ◽  
Thermal Fluctuations ◽  
Solid Particles ◽  
Large Field ◽  
Interstellar Space ◽  
Interstellar Grains ◽  
Long Time ◽  
Satisfactory State ◽  
The Magnetic Field

For a Long Time the Davis-Greenstein Theory (ref. 1) has been generally considered an adequate explanation of the mechanism responsible for the alinement of interstellar grains and thus for the observed interstellar polarization. The magnetic field required to orient paramagnetic grains is apparently somewhat greater than 10-5 gauss, a relatively large field, but according to reference 2 ferromagnetic grains, proposed by the authors of reference 3, can be oriented by a field of only 10-7 gauss. These results indicate that orientation of interstellar grains is easily explained, even if the magnetic field in interstellar space is relatively weak.Unfortunately, this relatively satisfactory state of affairs has been upset by two developments. Firstly, the basic mechanism of magnetic relaxation proposed by Davis and Greenstein has been questioned by Dr. C. Kittel of the University of California, who has pointed out that the disorienting effect associated with thermal fluctuations of magnetization within the solid particles is ignored in the formulation of this mechanism.

scholarly journals Hybrid Simulation of Solar-Wind-Like Turbulence

Solar Physics ◽  
2019 ◽  
Vol 294 (11) ◽  
Author(s):  
D. Aaron Roberts ◽  
Leon Ofman
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
High Speed ◽  
Radial Flow ◽  
Initial Conditions ◽  
Thermal Fluctuations ◽  
Flow Speed ◽  
Initial State ◽  
Simplifying Assumptions ◽  
The Magnetic Field

Abstract We present 2.5D hybrid simulations of the spectral and thermodynamic evolution of an initial state of magnetic field and plasma variables that in many ways represents solar wind fluctuations. In accordance with Helios near-Sun high-speed stream observations, we start with Alfvénic fluctuations along a mean magnetic field in which the fluctuations in the magnitude of the magnetic field are minimized. Since fluctuations in the radial flow speed are the dominant free energy in the observed fluctuations, we include a field-aligned $v_{\|}(k_{\perp })$v∥(k⊥) with an $k^{ -1}$k−1 spectrum of velocity fluctuations to drive the turbulent evolution. The flow rapidly distorts the Alfvénic fluctuations, yielding spectra (determined by spacecraft-like cuts) transverse to the field that become comparable to the $k_{\|}$k∥ fluctuations, as in spacecraft observations. The initial near constancy of the magnetic field is lost during the evolution; we show this also takes place observationally. We find some evolution in the anisotropy of the thermal fluctuations, consistent with expectations based on Helios data. We present 2D spectra of the fluctuations, showing the evolution of the power spectrum and cross-helicity. Despite simplifying assumptions, many aspects of simulations and observations agree. The greatly faster evolution in the simulations is at least in part due to the small scales being simulated, but also to the non-equilibrium initial conditions and the relatively low overall Alfvénicity of the initial fluctuations.

Flexural Wave Scattering at a Through Crack in a Conducting Plate Under a Uniform Magnetic Field

1997 ◽  
Vol 64 (4) ◽  
pp. 828-834 ◽  
Author(s):  
Y. Shindo ◽  
I. Ohnishi ◽  
S. Tohyama
Keyword(s):  
Magnetic Field ◽  
Integral Equations ◽  
Uniform Magnetic Field ◽  
Fourier Transforms ◽  
Flexural Wave ◽  
Crack Plane ◽  
Dual Integral Equations ◽  
Conducting Plate ◽  
Time Harmonic ◽  
The Magnetic Field

Following a classical plate bending theory of magneto-elasticity, we consider the scattering of time-harmonic flexural waves by a through crack in a conducting plate under a uniform magnetic field normal to the crack surface. An incident wave giving rise to moments symmetric about the crack plane is applied. It is assumed that the plate has the electric and magnetic permeabilities of the free space. By the use of Fourier transforms we reduce the problem to solving a pair of dual integral equations. The solution of the dual integral equations is then expressed in terms of a Fredholm integral equation of the second kind. The dynamic moment intensity factor versus frequency is computed and the influence of the magnetic field on the normalized values is displayed graphically. It is found that the existence of the magnetic field produces higher singular moments near the crack tip.

scholarly journals Thermally populated versus field-induced triplon bound states in the Shastry-Sutherland lattice SrCu2(BO3)2

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Dirk Wulferding ◽  
Youngsu Choi ◽  
Seungyeol Lee ◽  
Mikhail A. Prosnikov ◽  
Yann Gallais ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Raman Spectroscopy ◽  
External Magnetic Field ◽  
Ground State ◽  
High Field ◽  
Bound States ◽  
Thermal Fluctuations ◽  
Low Energy ◽  
Singlet Ground State ◽  
The Magnetic Field

AbstractThe Shastry–Sutherland compound SrCu2(BO3)2 constituting orthogonally coupled dimers harbors an S = 0 singlet ground state. The confluence of strong interdimer interaction and frustration engenders a spectrum of low-energy excitations including localized triplons as well as singlet and triplet bound states. Their dynamics are controlled by an external magnetic field and temperature. Here, we employ high-field Raman spectroscopy to map the field and temperature evolution of such bosonic composite quasiparticles on approaching the 1/8 magnetization plateau. Our study unveils that the magnetic field and thermal fluctuations show remarkably similar effects in melting the singlet bound states, but are disparate in their effects on the fine spectral shapes. This, together with the anti-crossing of two singlet bound states in the intermediate field B = 10 − 16 T, is discussed in terms of the correlated dynamics of frustrated, interacting bosons.

A theory of incoherent scattering of radio waves by a plasma II. Scattering in a magnetic field

1961 ◽  
Vol 263 (1313) ◽  
pp. 238-258 ◽  
Keyword(s):  
Magnetic Field ◽  
Frequency Spectrum ◽  
Exact Result ◽  
Thermal Fluctuations ◽  
Scattered Signal ◽  
Radio Waves ◽  
Doppler Shifts ◽  
Analytic Expressions ◽  
Nyquist Noise ◽  
The Magnetic Field

A general expression for the frequency spectrum of radio waves scattered by the random thermal fluctuations of electron density in a plasma in a magnetic field is derived. The derivation is based on the generalized Nyquist noise theorem used in part I. The exact result is then; simplified by means of an approximation which amounts to assuming the velocity of light to be infinite. It is shown that this approximation is quite adequate for ionospheric applications of the theory. Next it is proved, without appealing to any approximation, that the magnetic held can never alter the total scattered signal power; it can only redistribute this power over the spectrum. Finally, the detailed shape of the frequency spectrum of the scattered signal is examined. Analytic expressions are given for certain limiting cases, but for the cases of most interest, numerical methods must be used. The results of some numerical calculations are shown in figures 1 and 2. From these results, it can be seen that the magnetic field has a significant effect on the shape of the spectrum only if the incident radio beam is very nearly orthogonal to the magnetic lines of force. For example, for an operating frequency of 40 Mc/s, no significant magnetic effect is observed even when the beam is within 5 of orthogonality. As this angle is decreased further, however, the spectrum rapidly begins to develop spikes at Doppler shifts which are approximate multiples of the ion gyro-frequency. These spikes are quite pronounced when the beam is 2° from orthogonality. At higher operating frequencies, the beam must be proportionally closer to orthogonality to achieve the same effect.

AC FLUCTUATION CONDUCTIVITY IN TYPE-II SUPERCONDUCTORS

2012 ◽  
Vol 26 (22) ◽  
pp. 1250143
Author(s):  
BUI DUC TINH ◽  
LE MINH THU
Keyword(s):  
Magnetic Field ◽  
Gaussian Approximation ◽  
Thermal Fluctuations ◽  
Vortex Pinning ◽  
Abrikosov Vortex ◽  
Type Ii ◽  
Ginzburg Landau ◽  
Fluctuation Conductivity ◽  
Type Ii Superconductor ◽  
The Magnetic Field

We use the time-dependent Ginzburg–Landau to calculate AC fluctuation conductivity in type-II superconductor in 2D model under magnetic field. Thermal fluctuations are assumed to be strong enough to melt the Abrikosov vortex lattice created by the magnetic field into a vibrating vortex liquid and marginalize the effects of the vortex pinning by inhomogeneities. The nonlinear interaction term in dynamics is treated within self-consistent Gaussian approximation. We obtain expressions the complex conductivity and resistivity summing all Landau levels which are applicable essentially to whole liquid phase and are compared to experimental data on high-Tc superconductor Bi 2 Sr 2 CaCu 2 O 8+δ.

Dynamic Singular Moments in a Perfectly Conducting Mindlin Plate With a Through Crack Under a Magnetic Field

1998 ◽  
Vol 67 (3) ◽  
pp. 503-510 ◽  
Author(s):  
Y. Shindo ◽  
I. Ohnishi ◽  
S. Toyama
Keyword(s):  
Magnetic Field ◽  
Integral Equations ◽  
Fourier Transforms ◽  
Mindlin Plate ◽  
Crack Plane ◽  
Flexural Waves ◽  
Dual Integral Equations ◽  
Conducting Plate ◽  
Time Harmonic ◽  
The Magnetic Field

Following Mindlin’s theory of plate bending of magnetoelasticity, we consider the scattering of time-harmonic flexural waves by a through crack in a perfectly conducting plate under a uniform magnetic field normal to the crack surface. An incident wave giving rise to moments symmetric about the crack plane is applied. It is assumed that the plate has the electric and magnetic permeabilities of the free space. By the use of Fourier transforms we reduce the problem to solving a pair of dual integral equations. The solution of the dual integral equations is then expressed in terms of a Fredholm integral equation of the second kind. The dynamic moment intensity factor versus frequency is computed and the influence of the magnetic field on the normalized values is displayed graphically. It is found that the existence of the magnetic field produces lower singular moments near the crack tip. [S0021-8936(00)02603-9]

Observing the galactic magnetic field

1967 ◽  
Vol 31 ◽  
pp. 375-380
Author(s):  
H. C. van de Hulst
Keyword(s):  
Magnetic Field ◽  
Fair Agreement ◽  
Solar Neighbourhood ◽  
Galactic Magnetic Field ◽  
The Magnetic Field

Various methods of observing the galactic magnetic field are reviewed, and their results summarized. There is fair agreement about the direction of the magnetic field in the solar neighbourhood:l= 50° to 80°; the strength of the field in the disk is of the order of 10-5gauss.

Sign in / Sign up

Export Citation Format

Share Document