| 词汇 | example_english_field-lines |
| 释义 | Examples of field linesThese examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors. The fieldlines of the background fields lie on constant -planes; the relations (35)- (38) allow a great variety for their shapes. It reduces the two-dimensional to a one-dimensional problem, leaving only derivatives along the fieldlines. In the core of the flow the leading-order dependence of all fluid variables along the magnetic fieldlines can be described analytically for many problems. This vorticity is clearly such as to inhibit motion of the fluid across the magnetic fieldlines (see figure 5). The axial magnetic fieldlines are thus compressed and will conserve their flux throughout the implosion. In this paper, we have explored, on the basis of laboratory experiments, the creation of a flux tube with twisted magnetic fieldlines. Knowing this one finds immediately that the inertial correction to the electric potential has a parabolic behaviour along magnetic fieldlines. The plasma pressed by the magnetic field to the internal electrode is unstable because of an unfavorable curvature of the magnetic fieldlines. Because the magnetic fieldlines resist "bending," such azimuthal asymmetries are not expected to grow and become unstable. In a magnetized plasma, we have a natural symmetry axis along the direction of the magnetic fieldlines. The poloidally closed grid lines again coincide with magnetic fieldlines. The magnetic fieldlines, however, are no longer plane. The other class comprises equilibria with straight magnetic axis and fieldlines lying in planes orthogonal to the axis. Figure 9 shows the magnetic fieldlines at the six instants. This approach is formally equivalent to the determination of magnetic fieldlines, which satisfy the same mathematical equations. The third plot shows the fieldlines when the filament almost reaches its maximum depth into the magnetosphere. This distribution is such that the particles have no motion along the magnetic fieldlines, and this is too artificial for practical purposes. The latter situation would invoke a strong magnetic pressure gradient, leading to a pinch effect perpendicular to the external magnetic fieldlines. A discrete symmetry like mirror symmetry is not necessary, nor do fieldlines have to be plane. When > 0, (2.2) and (2.3) make it possible to model a sufficiently broad class of magnetic fields with a dipole-like configuration of fieldlines. Combining the internal plasma current and external coil currents, we generate twisted magnetic fieldlines in the plasma. Magnetic reconnection occur s when fieldlines are brought together, break and rejoin with other fieldlines. The magnetic fieldlines are shown to constitute geodesics on the constant total pressure surfaces. As the electrons spiral along the fieldlines, they remain close to the surface on which they were launched. We have in this paper shown how the parallel electric field is built up on auroral fieldlines. The twist of fieldlines is given by a current that is directed parallel with respect to the magnetic field, satisfying the forcefree condition. This only fails for fieldlines ejected from the sheet, which form a smaller portion of the volume. The nonlinear dynamics and structure of plasmas with tightly twisted magnetic fieldlines have been studied using a toroidal plasma device. Here a parabolic variation of potential along magnetic fieldlines is found as a weak correction to a quasi-two-dimensional flow. Moreover, the magnetic fieldlines map out circular, concentric magnetic surfaces. The fieldlines to be shown in this paper are actually the projections of fieldlines onto the simulation plane. The outflow material ejected from the disk surface is collimated by the twisted magnetic fieldlines, which are created by the rotation of the disk. The white lines of the left panel are magnetic fieldlines, those of right panel are lines of poloidal current density. Scalar fields defined on some reference surface are chosen to be constant along magnetic fieldlines. The magnetic field is again purely toroidal, but fieldlines are no longer planar. In other words, one does not want magnetic fieldlines that connect the plasma interior to the bounding walls of the fusion device. The heated products are directed out magnetic fieldlines to produce thrust. If the perturbation is too strong, stochastic wandering of the fieldlines throughout the confinement region can ensue. The resistive instability is due to the diffusion and rearrangement of the magnetic fieldlines, while the plasma resistivity is small. Remarkably, up to a trivial scaling, the geometry of the flux surfaces and magnetic fieldlines is unique. The fieldlines are straight and parallel to the current sheet. Their analogue in finite domains is not so clear, although they are reminiscent ballooning modes, which are localized on fieldlines of infinite length. Classical transport occur s when particle g yromotions around the magnetic fieldlines are randomly disturbed by collisions. Therefore, the eigenfunctions and polarizations of the resonant modes on these fieldlines are not expected to be symmetric. The fluid boundary layer is distorted and stretched along the fieldlines as is the induced magnetic field. We report here our attempts to explore, based on laboratory plasma experiments, the nonlinear dynamics of ' twisted magnetic fieldlines ' in their most common structure. In our experiment, we produced a toroidal flux tube with twisted magnetic fieldlines by applying helicity using an induction electric field. This is an example of the well-known result that the ions dominate the temperature-gradient-driven heat flux across magnetic fieldlines in a magnetized plasma. The above results provide a set of explicit criteria for the behavior of fieldlines in the composite turbulence model. In this way one could specify a perturbation that is initially perpendicular to the magnetic fieldlines of this fixed helicity. For nonstochastic fieldlines, the term 'integrable' is used, and the field-line invariants in such cases are associated with magnetic surfaces. In contrast to the uniform case, now antiparallel fieldlines are pushed together there. Indeed, fieldlines are pushed away from the centre of the layer and are stretched by the vortical flow. At the same time, fieldlines are pushed closer together in those regions at the interface where the flow converges and thereby enhances the density. As such, the detailed relation between this expression and more familiar ones based on straight magnetic fieldlines is not immediately clear. In this configuration, the magnetic fieldlines are almost parallel to the toroidal electric field. After resistive reconnection of fieldlines, the plasma recovers the original symmetry, and finally q(0) increases near the axis up to m\. This method visualizes a three-dimensional vector field by ribbon-like surfaces created by multiple fieldlines started from a line segment. Some measurements indicate that the electrostatic pulses are localized not only along the geomagnetic fieldlines, but also perpendicular to the geomagnetic field. The mirror symmetry prevents ergodization of fieldlines. They contain no free function and fieldlines are not planar. Three-dimensional magnetic fieldlines are rendered as streamlines, and the color of any scalar variables can be mapped on them (pressure or magnetic field component). In general, the flux surfaces are 'ergodic' in that the flux surfaces are covered by single magnetic fieldlines. This is because electrons can move very rapidly along the fieldlines while the ions are massive enough to cross the fieldlines. Due to the large thermal conductivity along magnetic fieldlines, plasma depletion becomes more and more elongated. One reason of these instabilities is density fluctuations produced due to oscillation of magnetic fieldlines under plasma and restoring force of magnetic fieldlines. This occurs near resonances of the magnetic fieldlines. If the ions travel along the magnetic fieldlines, the shortest path to reach the observation volume at this cross-section is in the counterclockwise direction. This process can be described as propagation of momentum and vorticity along magnetic fieldlines. In this case there is the plasma near the internal electrode that is unstable because of an unfavorable curvature of the magnetic fieldlines. An important point here is the accurate description of regions with complex (eventually ergodic) topology of the magnetic fieldlines. The curvature of the magnetic fieldlines is neglected in our model equations. Non-thermal whistlers are usually guided along the geomagnetic fieldlines where they travel from one hemisphere to another. For the fundamental modes of fieldlines without torsion, only one change in curvature is expected. A unique feature of our experiment, in comparison with other laboratory systems, is in that the twist of magnetic fieldlines is rather tight. This feature is not present in the four other fieldlines under examination. With the coil inside the plasma, it was possible to drive plasma currents using the outer magnetic fieldlines of the rotating dipole magnetic field. The grid lines that are closed around the axis coincide with magnetic fieldlines. The magnetic fieldlines here are parallel to the computational plane. For the collisionless limit, the transport depends strongly on the behaviour of magnetic fieldlines. This surface is mapped along fieldlines into the ionosphere, into the region of the main ionospheric trough. The magnetic fieldlines constitute geodesics on the flux surfaces. These examples are from corpora and from sources on the web. Any opinions in the examples do not represent the opinion of the Cambridge Dictionary editors or of Cambridge University Press or its licensors. |
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