Stability of a cold plasma traversed by two electron beams in the presence of an external magnetic field

1969 ◽  
Vol 47 (3) ◽  
pp. 249-256
Author(s):  
R. Jayakaran Isaac
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Short Wavelength ◽  
Cold Plasma ◽  
Electron Beams ◽  
Dispersion Relations ◽  
Wave Number ◽  
Longitudinal Modes ◽  
Transverse Modes ◽  
The Stability

In this paper, the stability of a cold plasma traversed by two electron beams in the presence of an external magnetic field is investigated. Dispersion relations for both longitudinal and transverse modes have been obtained. These dispersion relations have been discussed with respect to the two limiting cases of long- and short-wavelength disturbances. Apart from this, the dispersion relation for transverse modes has been solved numerically for a number of cases. It is found that the system becomes unstable against long-wavelength disturbances while it is stable against short-wavelength disturbances. In particular, for longitudinal modes, those perturbations whose wavelengths are such that their frequencies are near the corresponding frequencies of either of the two beams are found to be unstable. It is also found, numerically, in the case of transverse modes, that under certain conditions there exists a critical value of the wave number α, say α*, such that the system is unstable for the perturbations whose wave numbers satisfy the condition α < α*.

Electromagnetic ion-beam instabilities in a cold plasma

1996 ◽  
Vol 55 (1) ◽  
pp. 77-86 ◽  
Author(s):  
G. Gnavi ◽  
L. Gomberoff ◽  
F. T. Gratton ◽  
R. M. O. Galvão
Keyword(s):  
Magnetic Field ◽  
Dispersion Relation ◽  
External Magnetic Field ◽  
Cold Plasma ◽  
Ion Beam ◽  
Negative Energy ◽  
Left Hand ◽  
Right Hand ◽  
Polarized Waves ◽  
The Stability

We study the stability of the cold-plasma dispersion relation for circularly polarized waves in a plasma composed of an ion background and an ion beam. The presence of the beam introduces a resonant branch into the dispersion relation for right-hand-polarized waves propagating in the direction of the external magnetic field, which, for V>Vφ, has negative energy (here V is the beam velocityVφ is the wave phase velocity). Therefore this branch may give rise to explosive instabilities when the waves experience parametric decays. It is shown graphically that resonant right-hand-polarized and non-resonant left-hand-polarized waves, propagating parallel to the external magnetic field, can be unstable. It is also shown that the instability region can extend to large frequencies and wavenumnbers, and that the instability regions have a band structure. The parametric dependence of instability thresholds and marginal modes is also studied.

Convective instability of a plasma slab in a magnetic field

1980 ◽  
Vol 24 (3) ◽  
pp. 479-482 ◽  
Author(s):  
K. Bhimsen ◽  
Shivamoggi ◽  
Mahinder ◽  
S. Uberoi
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Convective Instability ◽  
Ionization Rate ◽  
Plasma Slab ◽  
The Stability

Convective instability of a plasma slab (contained between two metal walls) subject to a longitudinal external magnetic field is studied. The results show that (i) increase in the ionization rate Z causes a reduction in the stability of the plasma; (ii) the instability persists in the limit k ⇒ 0.

Hydromagnetic Stability of Two Rivlin-Ericksen Elastico-Viscous Superposed Conducting Fluids

1997 ◽  
Vol 52 (6-7) ◽  
pp. 528-532
Author(s):  
R. C. Sharma ◽  
P. Kumar
Keyword(s):  
Magnetic Field ◽  
Wave Number ◽  
Horizontal Magnetic Field ◽  
Number Range ◽  
Wave Number Range ◽  
Unstable Configuration ◽  
The Stability ◽  
Superposed Fluids ◽  
The Magnetic Field ◽  
Conducting Fluids

Abstract The stability of the plane interface separating two Rivlin-Ericksen elastico-viscous superposed fluids of uniform densities when the whole system is immersed in a uniform horizontal magnetic field has been studied. The stability analysis has been carried out, for mathematical simplicity, for two highly viscous fluids of equal kinematic viscosities and equal kinematic viscoelasticities. It is found that the stability criterion is independent of the effects of viscosity and viscoelasticity and is dependent on the orientation and magnitude of the magnetic field. The magnetic field is found to stabilize a certain wave-number range of the unstable configuration. The behaviour of growth rates with respect to kinematic viscosity and kinematic viscoelasticity parameters are examined numerically.

The effect of a radial magnetic field on the stability of Couette flow

1994 ◽  
Vol 72 (5-6) ◽  
pp. 258-265 ◽  
Author(s):  
M. A. Ali
Keyword(s):  
Magnetic Field ◽  
Eigenvalue Problem ◽  
Incompressible Fluid ◽  
Couette Flow ◽  
Wave Number ◽  
Rotating Cylinders ◽  
Radial Magnetic Field ◽  
Electrically Conducting ◽  
Angular Velocities ◽  
The Stability

The effect of a radial magnetic field on the stability of an electrically conducting incompressible fluid between two concentric rotating cylinders is considered. The eigenvalue problem for determining the critical Taylor number TC and the corresponding wave number aC is solved numerically for different values of ±μ(= Ω2/Ω1), (where Ω1, and Ω2 are me angular velocities of the inner and outer cylinders, respectively) and for different gap sizes. It is observed that the radial magnetic field stabilizes the flow. This effect is more pronounced for cylinders that are corotating as compared with counter-rotating cylinders or the situation where only the inner one is rotating.

Effect of External Magnetic Field Loaded at the Initial Period of Inertial Stretching Stage on the Stability of Shaped Charge Jet

2017 ◽  
Vol 45 (5) ◽  
pp. 875-881 ◽  
Author(s):  
Bin Ma ◽  
Zhengxiang Huang ◽  
Qiangqiang Xiao ◽  
Xudong Zu ◽  
Xin Jia ◽  
...  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Initial Period ◽  
Shaped Charge ◽  
The Stability ◽  
Shaped Charge Jet

Generalized dispersive Alfvén waves

2000 ◽  
Vol 64 (2) ◽  
pp. 125-130 ◽  
Author(s):  
P. K. SHUKLA ◽  
L. STENFLO
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Magnetic Field Line ◽  
Auroral Zone ◽  
Alfven Waves ◽  
Skin Depth ◽  
Dispersion Relations ◽  
Alfvén Waves ◽  
Electrostatic Waves ◽  
Kinetic Alfvén Waves

Generalized dispersion relations for Alfvén waves are derived, accounting for arbitrary values of ω/ωci, k⊥ρi, and k⊥λe, where ω(ωci) is the wave (ion gyro) frequency, k⊥ = 2π/λ⊥ the perpendicular (to the external magnetic field line) wavenumber, and ρi(λe) the ion gyroradius (electron skin depth). Our dispersion relations are appropriate for deducing the relationships of the dispersive (inertial and kinetic) Alfvén waves with other plasma modes. The present results can be considered as a prerequisite for understanding some salient features of the broadband electromagnetic/electrostatic waves that are frequently observed by the Freja and FAST spacecraft in the auroral zone of the Earth's ionosphere.

scholarly journals Dispersion relation analysis of turbulent magnetic field fluctuations in fast solar wind

2013 ◽  
Vol 31 (11) ◽  
pp. 1949-1955 ◽  
Author(s):  
C. Perschke ◽  
Y. Narita ◽  
S. P. Gary ◽  
U. Motschmann ◽  
K.-H. Glassmeier
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
High Speed ◽  
Energy Transport ◽  
Normal Modes ◽  
Frequency Dispersion ◽  
Dispersion Relations ◽  
Wave Number ◽  
Magnetic Fluctuations ◽  
Speed Solar Wind

Abstract. Physical processes of the energy transport in solar wind turbulence are a subject of intense studies, and different ideas exist to explain them. This manuscript describes the investigation of dispersion properties in short-wavelength magnetic turbulence during a rare high-speed solar wind event with a flow velocity of about 700 km s−1 using magnetic field and ion data from the Cluster spacecraft. Using the multi-point resonator technique, the dispersion relations (i.e., frequency versus wave-number values in the solar wind frame) of turbulent magnetic fluctuations with wave numbers near the inverse ion inertial length are determined. Three major results are shown: (1) the wave vectors are uniformly quasi-perpendicular to the mean magnetic field; (2) the fluctuations show a broad range of frequencies at wavelengths around the ion inertial length; and (3) the direction of propagation at the observed wavelengths is predominantly in the sunward direction. These results suggest the existence of high-frequency dispersion relations partly associated with normal modes on small scales. Therefore nonlinear energy cascade processes seem to be acting that are not described by wave–wave interactions.

Thermomagnetic convection in a layer of ferrofluid placed in a uniform oblique external magnetic field

2015 ◽  
Vol 764 ◽  
pp. 316-348 ◽  
Author(s):  
Habibur Rahman ◽  
Sergey A. Suslov
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Additional Parameter ◽  
Thermomagnetic Convection ◽  
Uniform External Magnetic Field ◽  
Inclination Angles ◽  
Convection Patterns ◽  
The Stability ◽  
The Magnetic Field ◽  
Field Inclination

AbstractLinear stability of magnetoconvection of a ferromagnetic fluid contained between two infinite differentially heated non-magnetic plates in the presence of an oblique uniform external magnetic field is studied in zero gravity conditions. The thermomagnetic convection that arises is caused by the spatial variation of magnetisation occurring due to its dependence on the temperature. The critical values of the governing parameters at which the transition between motionless and convective states is observed are determined for various field inclination angles and for fluid magnetic parameters that are consistently chosen from a realistic experimental range. It is shown that, similar to natural paramagnetic fluids, the most prominent convection patterns align with the in-layer component of the applied magnetic field but in contrast to such paramagnetic fluids the instability patterns detected in ferrofluids can be oscillatory. It is also found that, contrary to paramagnetic fluids, the stability characteristics of magnetoconvection in ferrofluids depend on the magnitude of the applied field which becomes an additional parameter of the problem. This is shown to be due to the nonlinearity of the magnetic field distribution within the ferrofluid.

Sign in / Sign up

Export Citation Format

Share Document