摘要:

It is shown that the size of a charged particle’s drift orbit is squeezed, i.e., reduced, in a magnetic well in tokamak plasmas. The squeezing factor depends on the energy of the particle, being larger for higher‐energy particles. Therefore, for high‐energy particles, the size of the drift orbit depends only on the magnetic geometry. These energy‐independent drift orbits are also observed [J. A. Rome and Y.‐K. M. Ping, Nucl. Fusion19, 1193 (1979)]. The implications on the core confinement improvement physics and the confinement of the advanced fuel are discussed. ©1996 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.871642

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Profiles of the noninductive current, driven by direct electron absorption of fast waves in the ion cyclotron range of frequencies, have been determined for DIII‐D tokamak discharges [Luxonetal.,PlasmaPhysicsandControlledNuclearFusionResearch, 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 159]. The results clearly indicate the presence of centrally peaked driven current and validate theoretical models of fast wave current drive. ©1996 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.871643

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Electric and magnetic self‐fields can exist in the rotating plasma. A self‐sustained rotation can be established in the plasma. The disturbed distribution function of rotating plasma is derived from the Vlasov equation. The propagation of waves in rotating plasma differs from that in the usual plasma. New terms for Landau damping appear. The local rotational behavior may become prevailing. ©1996 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.871644

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A scheme that allows stable confinement of a weakly ionized non‐neutral plasma is discussed. The method requires the forced rotation of the neutral gas within the trap about an axis that roughly coincides with the trap’s magnetic and mechanical axes. A number of the basic equilibrium and nonequilibrium properties of such a trapped plasma are calculated. ©1996 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.871645

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Multimode solitons are observed to be excited in an ion‐beam–plasma system. But, the excitation of some mode solitons of these is found to be suppressed under a certain condition depending on the density and velocity of a low‐energy ion beam, produced by the applied negative pulse. Furthermore, weak interaction between the slow‐beam soliton and ion‐acoustic soliton is also observed to cause small time lags in their trajectories on the distance–time plane. ©1996 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.871646

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A simple shearless model for collisional drift waves in low‐temperature plasmas is analyzed to point at fluctuation‐induced anomalous plasma transport. Spatially coherent structures do play an important role in the particle transport beyond a critical magnetic field strength. The transition from collisional to fluctuation‐induced transport is investigated. Special emphasis is put on analytical models for understanding the transition. The results from numerical simulations are interpreted. ©1996 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.871647

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Employing the two‐fluid model, a generalized Sagdeev equation governing solitary kinetic Alfve´n waves (SKAWs) and the criterion for the existence of SKAWs, which are valid for different ranges of plasma pressure parameter &bgr;, are presented. In the limit cases of &bgr;≫me/miand &bgr;≪me/mi, the present results correspond, respectively, with conclusions obtained by Hasegawaetal. [Phys. Rev. Lett.37, 690 (1976)] and by Shuklaetal. [J. Plasma Phys.28, 125 (1982)], that is, SKAWs accompanied by, respectively, hump and dip density solitons for &bgr;≫me/miand &bgr;≪me/mi. However, for the case of &bgr;∼me/mi, the present results show that SKAWs accompanied by both hump and dip density solitons are possible, and lead to KdV solitons in the small amplitude limit. In addition, the possibility for applying these results to electromagnetic spikes observed by the Freja scientific satellite is discussed [detailed information about the Freja satellite experiments can be found in serial papers presented in Space Sci. Rev.70, Nos. 3/4 (1994)]. ©1996 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.871648

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

It was shown by Syrovatskii [Sov. Phys. JETP33, 933 (1971)] that a perfectly conducting two‐dimensional magnetic field stressed externally develops a current sheet at an X point. A generalization of this analysis shows that a generic three‐dimensional magnetic field develops a closed ribbon of current along separators already existing in the field. A separator is a field line that begins and ends at different magnetic null points. A current ribbon will occur if there are two distinct separators beginning and ending at the same two nulls, thus forming a loop. The magnetic field containing the current ribbon is in force‐free equilibrium. An expression is found for the net current induced in the ribbon, and the magnetic energy stored by it, in terms of the amount of external stress. An electric field parallel to the current will facilitate reconnection and will dissipate the current and release the stored energy. ©1996 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.871627

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A theory for the growth of the double tearing mode in the early nonlinear stage is presented. The equations governing the nonlinear evolution of double tearing modes are formulated and are solved in different parameter regimes. When the phase difference between the two islands is &pgr;, the coupling of the two islands plays a destabilizing role. The island growth is of the formw∼tin the early nonlinear stage. The instability condition for the nonlinear double tearing mode is found, and is the same as that for the linear double tearing mode. When current profile is flattened near the two rational surfaces, the coupling plays the dominant role in determining the nonlinear growth.©1996 American Institute of Physics

ISSN:1070-664X    

DOI:10.1063/1.871649

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A model for plasma transport near marginal stability is presented. The model is based on subcri‐ tical resistive pressure‐gradient‐driven turbulence. Three‐dimensional nonlinear calculations based on this model show effective transport for subcritical mean profiles. This model exhibits some of the characteristic properties of self‐organized criticality. Perturbative transport techniques are used to elucidate the transport properties. Propagation of positive and negative pulses is studied. The observed results suggest a possible explanation of the apparent nonlocal effects ob‐ served with perturbative experiments in tokamaks. ©1996 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.871650

出版商:AIP    

年代:1996

数据来源: AIP