Electrostatic waves potential at the plasma and upper-hybrid resonances

1981 ◽  
Vol 25 (2) ◽  
pp. 239-254 ◽  
Author(s):  
J. Thiel ◽  
R. Debrie
Keyword(s):  
Magnetic Field ◽  
Kinetic Theory ◽  
Dispersion Equation ◽  
Cyclotron Frequency ◽  
Plasma Frequency ◽  
Electrostatic Waves ◽  
Ion Motion ◽  
Hybrid Resonance ◽  
Resonance Frequencies ◽  
The Magnetic Field

The potential created by an infinitesimal alternating dipole in a Maxwellian magnetoplasma is computed numerically at the plasma and upper-hybrid resonance frequencies when the latter extends from one to three times the electron cyclotron frequency. A linear full kinetic theory is used for a homogeneous magnetoplasma for which the forced ion motion and the collisions are neglected. The integral which gives the potential is evaluated by using the least-damping- roots (LDR) approximation, i.e. by neglecting the higher-order roots of the dispersion equation for electrostatic waves. Some characteristic potential patterns of dipoles parallel and perpendicular to the magnetic field are computed and comparisons with analytical results previously published are made. The numerical and analytical patterns are similar only at the plasma frequency when the dipole is parallel to the magnetic field.

Magnetic stabilization of transverse plasma instabilitiest

1971 ◽  
Vol 5 (3) ◽  
pp. 467-474 ◽  
Author(s):  
B. Buti ◽  
G. S. Lakhina
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Cyclotron Frequency ◽  
Plasma Frequency ◽  
Electron Plasma ◽  
Wave Number ◽  
Uniform External Magnetic Field ◽  
Magnetic Stabilization ◽  
Streaming Velocity ◽  
The Magnetic Field

Waves, propagating transverse to the direction of the streaming of a plasma in the presence of a uniform external magnetic field, are unstable if the streaming exceeds a certain minimum value. The magnetic field reduces the growth rate of this instability, and also increases the value of the minimum streaming velocity, above which the system is unstable. The thermal motions in the plasma, however, tend to stabilize the system if the magnetic field is weak (i.e. , Ω being the electron cyclotron frequency, k the characteristic wave-number, and Vt the thermal velocity); but, in case of strong magnetic field (i.e. ), they increase the growth rate, provided (ωp being the electron plasma frequency).

Stability of anisotropic plasmas to almost-perpendicular magnetosonic waves

1971 ◽  
Vol 6 (3) ◽  
pp. 495-512 ◽  
Author(s):  
R. W. Landau† ◽  
S. Cuperman
Keyword(s):  
Magnetic Field ◽  
Dispersion Relation ◽  
Simple Form ◽  
Cyclotron Frequency ◽  
Plasma Frequency ◽  
Alfven Wave ◽  
Larmor Radius ◽  
Ion Plasma ◽  
The Stability ◽  
The Magnetic Field

The stability of anisotropic plasmas to the magnetosonic (or right-hand compressional Alfvén) wave, near the ion cyclotron frequency, propagating almost perpendicular to the magnetic field, is investigated. For this case, and for wavelengths larger than the ion Larmor radius and for large ion plasma frequency (w2p+ ≫ Ωp+) the dispersion relation is obtained in a simple form. It is shown that for T # T' (even T ≫ T) no instabifity occurs. The resonant ters are also included, and it is shown that there is no resonant instabifity, only damping.

Optical Mixing in a Magnetized Plasma

1971 ◽  
Vol 49 (16) ◽  
pp. 2187-2193 ◽  
Author(s):  
J. Meyer ◽  
B. Stansfield
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Spectral Density ◽  
Electromagnetic Waves ◽  
Basic Assumption ◽  
Magnetized Plasma ◽  
Ion Motion ◽  
Resonance Frequencies ◽  
Optical Mixing ◽  
The Magnetic Field

The nonlinear interactions of two electromagnetic waves resulting in the excitation of electrostatic oscillations in a magnetized homogeneous plasma are studied. A general expression for the spectral density of the induced fluctuations is derived which includes the effect of the ion motion and an externally applied uniform magnetic field. One basic assumption made is that the frequencies of the electromagnetic waves are much larger than any of the plasma resonance frequencies. Numerical calculations are carried out for the specific case where the induced k vector is parallel to the external magnetic field and the results are presented in a series of graphs. The effect of the ion motion for this case is discussed in detail. Some aspects of the case where the induced k vector is perpendicular to the magnetic field are also discussed. It is found that both—the ion motion and an external magnetic field—can significantly influence the spectral density of the fluctuations.

Ion-acoustic instabilities driven by an ion velocity ring

1985 ◽  
Vol 34 (3) ◽  
pp. 467-479 ◽  
Author(s):  
K. Akimoto ◽  
K. Papadopoulos ◽  
D. Winske
Keyword(s):  
Magnetic Field ◽  
Electron Temperature ◽  
Dispersion Equation ◽  
Plasma Frequency ◽  
Ion Temperature ◽  
Ion Distribution ◽  
Electrostatic Waves ◽  
Ion Plasma ◽  
Ion Acoustic ◽  
Acoustic Instabilities

A ring distribution of ions in velocity space can generate electrostatic waves which propagate predominantly along an ambient magnetic field at frequencies comparable with the ion plasma frequency. A dispersion equation which accounts for these waves is presented, and solved analytically and numerically. It was found that ion-acoustic-like waves are excited in a plasma even if the electron temperature is comparable with the ion temperature under the assumption of an anisotropic ion distribution.

scholarly journals Ion motion in the current sheet with sheared magnetic field – Part 1: Quasi-adiabatic theory

2013 ◽  
Vol 20 (1) ◽  
pp. 163-178 ◽  
Author(s):  
A. V. Artemyev ◽  
A. I. Neishtadt ◽  
L. M. Zelenyi
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Analytical Description ◽  
Particle Energy ◽  
Tangential Component ◽  
Adiabatic Invariant ◽  
Ion Motion ◽  
Adiabatic Theory ◽  
Fast Oscillations ◽  
The Magnetic Field

Abstract. We present a theory of trapped ion motion in the magnetotail current sheet with a constant dawn–dusk component of the magnetic field. Particle trajectories are described analytically using the quasi-adiabatic invariant corresponding to averaging of fast oscillations around the tangential component of the magnetic field. We consider particle dynamics in the quasi-adiabatic approximation and demonstrate that the principal role is played by large (so called geometrical) jumps of the quasi-adiabatic invariant. These jumps appear due to the current sheet asymmetry related to the presence of the dawn–dusk magnetic field. The analytical description is compared with results of numerical integration. We show that there are four possible regimes of particle motion. Each regime is characterized by certain ranges of values of the dawn–dusk magnetic field and particle energy. We find the critical value of the dawn–dusk magnetic field, where jumps of the quasi-adiabatic invariant vanish.

scholarly journals Ion motion in the current sheet with sheared magnetic field – Part 2: Non-adiabatic effects

2013 ◽  
Vol 20 (5) ◽  
pp. 899-919 ◽  
Author(s):  
A. V. Artemyev ◽  
A. I. Neishtadt ◽  
L. M. Zelenyi
Keyword(s):  
Magnetic Field ◽  
Current Sheet ◽  
Particle Motion ◽  
Phase Plane ◽  
Time Interval ◽  
Ion Motion ◽  
Average Value ◽  
Structure And Dynamics ◽  
Adiabatic Theory ◽  
The Magnetic Field

Abstract. We investigate dynamics of charged particles in current sheets with the sheared magnetic field. In our previouspaper (Artemyev et al., 2013) we studied the particle motion in such magnetic field configurations on the basis of the quasi-adiabatic theory and conservation of the quasi-adiabatic invariant. In this paper we concentrate on violation of the adiabaticity due to jumps of this invariant and the corresponding effects of stochastization of a particle motion. We compare effects of geometrical and dynamical jumps, which occur due to the presence of the separatrix in the phase plane of charged particle motion. We show that due to the presence of the magnetic field shear, the average value of dynamical jumps is not equal to zero. This effect results in the decrease of the time interval necessary for stochastization of trapped particle motion. We investigate also the effect of the magnetic field shear on transient trajectories, which cross the current sheet boundaries. Presence of the magnetic field shear leads to the asymmetry of reflection and transition of particles in the current sheet. We discuss the possible influence of single-particle effects revealed in this paper on the current sheet structure and dynamics.

Kinetic Alfvén solitons in a low-beta plasma

1997 ◽  
Vol 57 (2) ◽  
pp. 235-245 ◽  
Author(s):  
B. C. KALITA ◽  
R. P. BHATTA
Keyword(s):  
Magnetic Field ◽  
Mach Number ◽  
Solitary Waves ◽  
Magnetic Pressure ◽  
Hot Electrons ◽  
Mass Ratio ◽  
Ion Motion ◽  
Electron Inertia ◽  
Theoretical Investigations ◽  
The Magnetic Field

Kinetic Alfvén solitons with hot electrons and finite electron inertia in a low-beta (β=8πn0T/B2G, the ratio of the kinetic to the magnetic pressure) plasma is studied analytically, with the ion motion being considered dominant through the polarization drift. Both compressive and rarefactive kinetic Alfvén solitons are found to exist within a definite range of kz (the direction of propagation of the kinetic Alfvén solitary waves with respect to the direction of the magnetic field) for each pair of assigned values of β and M (Mach number). Unlike in previous theoretical investigations, β appears as an explicit parameter for the kinetic Alfvén solitons in this case. In addition, consideration of the electron pressure gradient is found to suppress the speed of both the Alfvén solitons considerably for A (=2QM2/βk2z, with Q the electron-to-ion mass ratio) less than unity.

THE ADMITTANCE OF AN INFINITE CYLINDRICAL ANTENNA IN A LOSSY INCOMPRESSIBLE, ANISOTROPIC PLASMA

1967 ◽  
Vol 45 (12) ◽  
pp. 4019-4038 ◽  
Author(s):  
Edmund K. Miller
Keyword(s):  
Magnetic Field ◽  
Free Space ◽  
Cyclotron Frequency ◽  
Plasma Frequency ◽  
Floating Potential ◽  
Space Layer ◽  
Cylindrical Antenna ◽  
Warm Plasma ◽  
Positive Ion ◽  
Uniform Plasma

A numerical investigation of the admittance of an infinite, circular cylindrical antenna excited at a circumferential gap of nonzero thickness, and immersed in a lossy incompressible magnetoplasma with the antenna parallel to the static magnetic field is described. A concentric free-space layer (the vacuum sheath) which separates the antenna from the external uniform plasma is included in the analysis to approximate the positive ion sheath which may form about a body at floating potential in a warm plasma. The numerical results for the antenna admittance show that: (1) in the absence of a sheath, a sharp admittance maximum is found at the electron cyclotron frequency, with the maximum more pronounced when the plasma frequency exceeds the cyclotron frequency than for the converse case; (2) the vacuum sheath shifts upward in frequency and reduces in amplitude the admittance maximum which occurs for the sheathless case at the cyclotron frequency; (3) a kink or minimum in the admittance is found at the plasma frequency.

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