摘要:

The evolution of electrostatic waves and excitation of instabilities in two-component streaming plasmas in a magnetic field are analytically studied. The modified spectrum and growth term of instability are derived to explain the physical situations like cold plasma, warm plasma, ion fusion aspect along with the uncoupled mode. The striking features of the analysis are displayed in the form of profiles of the refractive index (&eegr;) varying with particle thermal energy(KT)in different streaming regimes(V0).The effect of streaming enhances the frequency propagation of waves or dispersion, including phase velocity and refractive indices. However, the damping or growth term of instability is diminished, appreciably owing to the streaming. The findings may have important implications to space and magnetospheric settings where a beam–plasma interaction exists. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.873033

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Patchy magnetic reconnection involves transient field-aligned current filaments. The spatial localization, transient time-dependence, and orientation of these current filaments means they must radiate torsional Alfve´n waves. Radiation of wave energy does not come for free—it must load the current which acts as the radiative source. This loading (radiation resistance) is proposed as the energy sink required for collisionless magnetic reconnection to proceed. Radiation resistance for both inertial and kinetic Alfve´n waves is calculated and, for highly collisionless plasmas, is shown to exceed by a substantial factor both Spitzer resistivity and the effective resistance due to the direct acceleration of electrons (inertial loading). The radiation resistivity is shown to provide the magnetic field diffusivity required for magnetic fields to diffuse across the assumed width of the current filament on the time scale of the reconnection. It is also shown that Landau damping of the radiated waves results in the generation of energetic, field-aligned particles: in the&bgr;≪me/miregime the energetic particles are electrons while in theme/mi≪&bgr;≪1regime, the energetic particles are ions. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.873034

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The influence of flow shear and curvature on toroidal drift modes has been studied for the case of strong inhomogeneity where the ballooning mode formalism does not apply. It has been found that flow curvature is often as important as the flow shear and may lead to complete cancellation of magnetic shear damping. The limit of validity of the ballooning mode formalism is explored. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.873035

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

For axial symmetry, in this study we report on analytical solutions of the magnetohydrodynamics (MHD) equilibrium of a plasma within the magnetic environment of a point dipole. Inside the plasma domain, the magnetic flux function is calculated for a given shape of the pressure profile. Another magnetic flux function is derived outside the plasma domain, where the pressure vanishes. Both functions and their normal derivatives are continuous through the boundary between the two domains; together they constitute the solution of our problem. A pressure profile that is a quadratic function of the magnetic flux function is used. It leads to an exact solution which is a simple function of the spherical coordinates. It is shown that, in this situation, the plasma energy is distributed over the entire plasma domain. This solution is well suited as a magnetospheric model. The magnetic flux function determined outside the plasma domain is expressed by a very general formula that is valid for wide classes of both the pressure profiles and the shape of a plasma exterior boundary. Far away from this boundary, as near the coordinate center, the magnetic field tends to be dipolar. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.873036

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The kinetic equations for an interacting dust system with external time-dependent forces is considered from the Born–Bogolyubov–Green–Kirkwood–Yvon equations. A kinetic equation is obtained by writing the two-particle distribution function as a product of two one-particle distribution functions and the equilibrium radial distribution function. It is shown that a Vlasov-like equation is recovered with a collision term which is a functional of the pair correlation function. Wave behavior from the corresponding fluid equations is considered for a dusty plasma. The results are in qualitative agreement with previously obtained dispersion relations based on generalized hydrodynamics and the quasilocalized charge approximation. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.873037

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Oscillating patterns of nonlinear waves in a cold non-neutral magnetized plasma bounded by a spherical dielectric are obtained. These patterns, oroscillons, are composed of bulk and surface waves that are strongly but not resonantly coupled. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.873038

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Wave propagation in a dusty, magnetized, strongly inhomogeneous plasma at frequencies below the ion–cyclotron frequency, and near the dust cyclotron frequency, is considered. The dust grains are assumed to carry a proportion of the negative charge of the plasma. Wave resonances and cutoffs in a homogeneous plasma are discussed. The dispersion relation for surface waves propagating on an interface between a dusty plasma and a vacuum is derived and studied, and their connection to surface waves in general two-ion-species plasmas is analyzed. The damping of the waves due to Alfve´n resonance absorption in a narrow but nonzero width interface is derived, and it is shown that for a range of frequencies above the dust cyclotron frequency the surface wave can propagate undamped by resonance absorption. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.873039

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The mode transition from a capacitively coupled mode (Emode) to an inductively coupled mode (Hmode) was observed in an inductive Ar plasma source by applying an axially uniform lowBfield. The applied fundamental rf was 13.56 MHz and many harmonic components were observed. A beat and standing wave patterns of azimuthally symmetric(m=0mode) first and second harmonic pseudosurfaces and helicon waves were measured at various densities(n∼9.0×1010–2.2×1011 cm−3)andBfields (12–28 G). Wave propagation mode changes, from pseudosurface to helicon waves and from helicon to pseudosurface waves, were observed at critical conditions,&ohgr;c/&ohgr;>3.0andn∼2.2×1011 cm−3.©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.873040

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A controversy on the existence of continuous spectra of ideal magnetohydrodynamics in addition to the well-known Alfve´n and slow continua, dating back to a conjecture by Grad [Proc. Natl. Acad. Sci. USA70, 3377 (1973)] and revived by Lashmore-Davies, Thyagaraja, and Cairns [Phys. Plasmas4, 3243 (1997)], is once more resolved by demonstrating that the resolvent operator is bounded in the relevant domain: There are no additional continua. In addition, the solution of the initial value problem is constructed in terms of the three-dimensional Green's dyadic, which is free of apparent singularities and clearly exhibits the classical continua as &dgr; functions on the diagonal. This construction provides the connection with the proper and improper normal modes and shows that the local dynamics on the magnetic surfaces is described by the classical continua. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.873041

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The effect of ion drag on negatively charged dust grains is considered as a possible mechanism of excitation of the dust-acoustic (DA) ionization instability. It is found that DA waves are more and more damped as the coefficient for ion drag, &mgr;, increases from zero to a critical value,&mgr;crit.For&mgr;>&mgr;crita zero-frequency (nonpropagating) perturbation grows when the drag of the ions on the dust grains overcomes the effect of the perturbation electric field. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.873042

出版商:AIP    

年代:1998

数据来源: AIP