摘要:

A new, electrostatic, one‐dimensional plasma instability is described. It arises when an external electric field is applied to a cold plasma in which both species have initial density perturbations. Both computer simulations and fluid calculations have revealed the instability, which, for sufficiently large perturbations, has a growth rate greater than the two‐stream instability.

ISSN:0031-9171    

DOI:10.1063/1.1694843

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Particles in or near resonance with a plasma wave undergo perturbations of their equilibrium orbits due to stochastic fields. This contributes added diffusion damping to any wave in the plasma. In a steady‐state experiment this mechanism can cause the saturation of a wave. A theory of the current‐driven ion cyclotron instability modified by turbulent damping based on addition of a damping term to the linear dispersion relation is presented. The turbulent damping is interpreted as an upper bound on the linewidth of the wave. As current varies, the frequency and line width of the mode alter. Once the frequency of the ion cyclotron wave is lowered to nearly the ion cyclotron frequency, mode coupling to an ion‐acoustic wave seems to occur, damping the oscillations. Until this point, detailed predictions of theory agree well with experiment.

ISSN:0031-9171    

DOI:10.1063/1.1694804

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Current‐generated broadband turbulence can appear to individual particles as a diffusive damping, leading to saturation of low‐frequency modes in steady‐state experiments. Mode saturation occurs when the linear growth&ggr; = k⊥2D⊥,the diffusive damping. As long as mode frequency&ohgr; > k⊥2D⊥,the mode is well defined. Whenk⊥2D⊥ > &ohgr;,the mode loses meaning and should disappear. The turbulent dampingk⊥2D⊥is interpreted as an upper bound on the linewidth of the wave. As current increases, frequency falls and linewidth increases. The mode is quenched when damping exceeds the mode frequency. Agreement with experiment is good.

ISSN:0031-9171    

DOI:10.1063/1.1694805

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The angular distribution of particle velocities in a magnetized plasma can be uniquely determined by measurement of the variation of density along a magnetic field line. From measurements on the 2XII mirror experiment, it is determined that the angular distribution of ions is monotonic and very closely approximatessin2a&thgr;,wherea = 2.25and&thgr;is the pitch angle at the center. Particles with sin&thgr; < 0.72communicate with the region outside the mirrors and comprise approximately 5&percent; of the total density at the center.

ISSN:0031-9171    

DOI:10.1063/1.1694806

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The equilibrium of an axisymmetric, large aspect‐ratio, finite temperature toroidal plasma enclosed by a perfectly conducting toroidal container is studied analytically. The new feature of the analysis is the presence of a relativistic electron beam which circulates around the torus thus producing a poloidal magnetic field in addition to the external field and the field created by currents in the plasma. This problem may be of interest in connection with recent toroidal beam injection experiments at Cornell University and in tokamaks. The equilibria are obtained from the relativistic virial theorem. Specific examples are given wherein the plasma pressure is characterized by its dependence on the magnetic flux function and the relativistic electron beam is characterized by an electron distribution function which is a delta function in energy and canonical momentum in the toroidal direction.

ISSN:0031-9171    

DOI:10.1063/1.1694807

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

A generalized treatment of the three‐wave decay of oblique whistler/electron cyclotron waves into other whistler/electron cyclotron waves is presented which clarifies the three‐dimensional aspects of the process. The generalized expression for the growth rate is given and several special cases are considered, establishing the existence of a strong instability. It is shown that there is no instability when the three wavenumber axes are coplanar with the background magnetic field in the plane except for the special case when one of the waves propagates along the background magnetic field.

ISSN:0031-9171    

DOI:10.1063/1.1694808

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

Satellite soundings of the topside ionosphere reveal diffuse signals on the low frequency side ofnfHwhennfH < fT,wherenis an integer andfHandfTare the electron cyclotron and upper hybrid frequencies, respectively. They extend no further than the midway point between(n − 1)fHandnfH.The present observing conditions allow detection up ton = 10.The origin of the signals is attributed to the Harris instability of longitudinal plasma waves whenT⊥/T‖ > 2n,whereT⊥andT‖refer to the temperature corresponding to the electron motion perpendicular and parallel to the earth's magnetic field, respectively. The large anisotropies are caused by collisionless cyclotron damping of energy from the high power sounder pulse. This energy is absorbed in a region which extends radially from the antenna, a distance which is small compared with the antenna length but large compared with the antenna sheath region.

ISSN:0031-9171    

DOI:10.1063/1.1694809

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

From scaling arguments, the interfacial tension of the3He−4He system is expected to vanish as(Tc − T)2,as the tricritical point is approached.

ISSN:0031-9171    

DOI:10.1063/1.1694810

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The magnetohydrodynamic equilibrium of an elliptical, cylindrical plasma, with uniform current density, is not uniquely determined by the boundary conditions.

ISSN:0031-9171    

DOI:10.1063/1.1694811

出版商:AIP    

年代:1974

数据来源: AIP

摘要:

The momentum of photons in a collisionless plasma reproduces the Fresnel formulas only if the energy exchange with electrons is included. The transferred momenta correspond exactly to those derived from the theory of the nonlinear force of a laser‐plasma interaction.

ISSN:0031-9171    

DOI:10.1063/1.1694812

出版商:AIP    

年代:1974

数据来源: AIP