1,721,072 research outputs found
DYNAMO MECHANISM VIA DIFFUSIVE FLOW
No full textA diffusive flow for plasma transport is proposed as a new mechanism for a dynmo. Cowling pointed out that a flow which has a velocity relative to the magnetic field line is essential to the mechanism of a dynamo. From this point of view, the fluid motion associated with the plasma diffusion across the magnetic field has the potential to be a good dynamo mechanism. When anomalous diffusion and classical resistivity are adopted for a sunspot plasma, it is found in the small size sunspot model that an inward diffusive flow can effectively amplify the magnetic field on a time scale comparable to the observed growth rate.X115sci
Coronal heating by Alfven waves
No full textCoronal heating by Alfven waves is reexamined considering the effect of the the granular structure of the sun's surface. From the observation that the Alfven waves in the sun's atmosphere are originally generated by the surface granular motion, it is speculated that the coronal Alfven waves may possess the intrinsic transversal length scale of the granular size from the time of their generation. Thus, the dispersion relation for Alfven waves with a transversal variation has been calculated, incorporating Braginskii's expression of viscosity. As a result, it is found that there is a branch of Alfven waves which can be effectively damped by the viscosity, in addition to the branch of Alfven waves which are not damped. The short transversal length scale associated with the granular cells seems to have the potential to damp the Alfven waves effectively in the corona.X111sciescopu
Spin motive force and Faraday law for electrons in mesoscopic rings
No full textThe spin motive force and Faraday law for electrons due to the time-dependent Aharonov-Casher effect are studied by using the Goldhaber-Anandan gauge theory for a low energy spin particle. The spin motive force and Faraday law associated with the time-dependent magnetic field are also discussed based on the same gauge theory. The gauge theoretic approach provides a unified view for the various spin motive forces and spin Faraday laws.open1121sciescopu
Effects of the granular structure on the possible dissipation of Alfven waves in the sun
No full textIt is conjectured that the granular structure might play an important role in the coronal heating problem. It is found that, when the effect of the granular structure is incorporated, compressional Alfven waves could be damped effectively in the corona by the viscosity. The typical. granular size (about 1km) seems to be related to the Alfven wave damping near the bottom of the coronal region and the supergranular size to that in the upper region.X112sciescopu
Preferential acceleration and magnetic field enhancement in plasmas with e+/e- beam injection
No full textA theoretical model of current filaments predicting preferential acceleration/deceleration and magnetic field enhancement in a plasma with e(+)/e(-) beam injection is presented. When the e(+)/e(-) beams are injected into a plasma, current filaments are formed. The beam particles are accelerated or decelerated depending on the types of current filaments in which they are trapped. It is found that in the electron/ion ambient plasma, the e(+) beam particles are preferentially accelerated, while the e(-) beam particles are preferentially decelerated. The preferential particle acceleration/deceleration is absent when the ambient plasma is the e(+)/e(-) plasma. We also find that the particle momentum decrease can explain the magnetic field increase during the development of Weibel/filamentation instability. Supporting simulation results of particle acceleration/deceleration and magnetic field enhancement are presented. Our findings can be applied to a wide range of astrophysical plasmas with the e(+)/e(-) beam injection. (C) 2016 AIP Publishing LLC.110sciescopu
Dephasing rate and superconducting proximity
No full textWe show that the maximum penetration depth of the anomalous quasiclassical Green's function from a superconductor into an adjacent normal metal is directly related to the phase relaxation time tau(phi). The latter describes normal-metal phase correlations between two electrons with opposite spins. In the presence of spin-dependent interactions this phase relaxation time differs from the one found in weak localization corrections to the conductivity. The Josephson current measurements in a SINIS-structure could be used to determine tau(phi) experimentally.X111sciescopu
PERSISTENT SPIN CURRENTS INDUCED BY THE AHARONOV-CASHER EFFECT IN MESOSCOPIC RINGS
No full textopen1144sciescopu
A self-gravitating instability in a streaming dusty plasma
No full textWe study the linear instability of a self-gravitating dusty plasma in which dust particles stream with respect to the background electrons and ions. It is found that the self-excited magnetic fields induced by the dust particle's velocity perturbation can stabilize the plasma.X112sciescopu
Electron acceleration by a circularly polarized laser pulse in the presence of an obliquely incident magnetic field in vacuum
No full textLaser-induced acceleration of an electron injected initially at an angle to the direction of a circularly polarized laser pulse in the presence of an obliquely incident magnetic field has been investigated. For a suitable position of the peak of the laser pulse, the external magnetic field exists at an angle such that it can be parallel to the magnetic field of the laser pulse. The electron gains considerable energy and retains it even after passing of the laser pulse in the presence of an optimum magnetic field in vacuum. The electron attains the maximum amount of energy at a particular angle of the incident magnetic field due to the betatron resonance. (c) 2005 American Institute of Physics.open113528sciescopu
Amplification of axially symmetric magnetic field by Bohm particle diffusion
No full textThe magnetic induction equation for an axially symmetric magnetic field reveals an interesting feature, when the Bohm plasma diffusion is incorporated. The 1/B dependence of Bohm diffusion allows the induction equation to transform into a simple heat equation which admits an exact solution when the plasma temperature is constant. When the diffusion velocity satisfies a certain condition, the axially symmetric magnetic field can be significantly enhanced. (C) 2004 American Institute of Physics.open1110sciescopu
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