Ion-acoustic waves and radio aurora

1970 ◽  
Vol 48 (16) ◽  
pp. 1863-1873 ◽  
Author(s):  
D. R. McDiarmid
Keyword(s):  
Acoustic Wave ◽  
Electric Field ◽  
Acoustic Waves ◽  
Polarization Field ◽  
Wave Instability ◽  
Ion Acoustic Waves ◽  
Ion Acoustic Wave ◽  
Proposed Model ◽  
Ion Acoustic

A previously proposed model of radio aurora is developed further and is used to relate and explain data obtained during an event described by Hofstee and Forsyth. The basis of the model is the two-stream, ion-acoustic wave instability. Although the model explains this particular event very well, attempts to apply it to certain other experimental situations have resulted in unresolved difficulties. These are discussed briefly.During the Hofstee and Forsyth event a geomagnetic bay was observed north of the scattering region. An explanation of this bay using the electric field deduced from the radio backscatter data required the assumption of a polarization field within the band of enhanced plasma associated with the visual aurora present at the same location (Boström's model 1).

scholarly journals Effect of Negative Ions on the Instability of Ion-acoustic Waves in a Relativistic Plasma

1997 ◽  
Vol 50 (2) ◽  
pp. 319 ◽  
Author(s):  
K. K. Mondal ◽  
S. N. Paul ◽  
A. Roychowdhury
Keyword(s):  
Dispersion Relation ◽  
Acoustic Wave ◽  
Acoustic Waves ◽  
Negative Ions ◽  
Ion Concentration ◽  
Negative Ion ◽  
Relativistic Velocity ◽  
Ion Acoustic Waves ◽  
Ion Acoustic Wave ◽  
Ion Acoustic

The dispersion relation of an ion-acoustic wave propagating through a collisionless, unmagnetised plasma, having warm isothermal electrons and cold positive and negative ions has been derived. It is seen that the ion-acoustic wave will be unstable in the presence of streaming of ions. Instability of the wave is graphically analysed for the plasma having (H+, O¯) ions, (H+, O2¯) ions, (H+, SF5¯) ions, (He+, Cl¯) ions and (Ar+, O¯) ions with different negative ion concentration and relativistic velocity.

Reflection of ion-acoustic waves from bipolar potential structures

1989 ◽  
Vol 41 (2) ◽  
pp. 243-255 ◽  
Author(s):  
Y. Nakamura ◽  
Joyanti Chutia
Keyword(s):  
Acoustic Wave ◽  
Acoustic Waves ◽  
High Efficiency ◽  
Ion Beam ◽  
Plasma Potential ◽  
Ion Acoustic Waves ◽  
Ion Acoustic Wave ◽  
Plasma Device ◽  
Ion Acoustic ◽  
Double Plasma Device

Reflection of ion-acoustic waves from the ion sheath in front of the separation grid in a double-plasma device has been investigated experimentally. The plasma potential φ of the source plasma was controlled relative to that of the target plasma. When eφ < κΤe, where Τe is the electron temperature, no reflection was observed. The reason for this is that ions are drifting towards the grid with the Bohm velocity, i.e. the ion-acoustic velocity. When eφ > κΤe the reflected wave consists of the ion-acoustic wave and the ion beam mode. The reflection coefficient for the ion-acoustic wave is about unity. This high efficiency is due to reflection of the ions themselves.

Radio-auroral scattering at two closely spaced frequencies

1980 ◽  
Vol 58 (10) ◽  
pp. 1485-1491 ◽  
Author(s):  
I. P. W. Sinclair ◽  
P. A. Forsyth
Keyword(s):  
Acoustic Wave ◽  
Acoustic Waves ◽  
Ion Acoustic Waves ◽  
Ion Acoustic Wave ◽  
Individual Ion ◽  
Ion Acoustic ◽  
Wave Trains ◽  
Radio Frequencies

Two radio frequencies near 40 MHz and separated by 500 Hz were used to investigate the type of radio-auroral scattering which arises in ion-acoustic waves. The results confirm those of Haldoupis and Sofko who found that individual ion-acoustic wave trains have lifetimes of only tenths of seconds. In addition it was found that instantaneous signal amplitudes on these two frequencies were sometimes poorly correlated indicating the coexistence of widely separated ion-acoustic wave trains. It appears that the radio-auroral scattering region is typically large but within it individual ion-acoustic wave trains grow and decay rapidly. Significant periodicities were found in the signals and these are attributed to magnetospheric modulation of the auroral process.

Influence of High Frequency Electric Field on the Dispersion of Ion-Acoustic Waves in Plasma

1981 ◽  
Vol 36 (1) ◽  
pp. 17-22
Author(s):  
A. Turky ◽  
M. Čerček ◽  
R. Tavzes J. Stefan
Keyword(s):  
Electric Field ◽  
Acoustic Waves ◽  
High Frequency ◽  
Wave Dispersion ◽  
Plasma Stream ◽  
Ion Acoustic Waves ◽  
Ion Acoustic Wave ◽  
High Frequency Electric Field ◽  
Ion Acoustic ◽  
Frequency Electric Field

The modification of the ion-acoustic wave dispersion under the action of a high frequency electric field was studied experimentally, the wave propagating along and against the plasma stream. The frequency of the field amounted to approximately half the electron plasma frequency. It was found that the phase velocity of the ion wave and the plasma drift velocity decrease as the effective high frequency field power increases

scholarly journals Ion-Acoustic Instabilities in a Multi-Ion Plasma

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Noble P. Abraham ◽  
Sijo Sebastian ◽  
G. Sreekala ◽  
R. Jayapal ◽  
C. P. Anilkumar ◽  
...  
Keyword(s):  
Acoustic Wave ◽  
Acoustic Waves ◽  
Ion Acoustic Waves ◽  
Ion Acoustic Wave ◽  
Oxygen Ions ◽  
Ion Plasma ◽  
Thermal Spread ◽  
Ion Acoustic ◽  
Acoustic Instabilities ◽  
The Stability

We have, in this paper, studied the stability of the ion-acoustic wave in a plasma composed of hydrogen, positively and negatively charged oxygen ions, and electrons, which approximates very well the plasma environment around a comet. Modelling each cometary component (H+, O+, and O−) by a ring distribution, we find that ion-acoustic waves can be generated at frequencies comparable to the hydrogen ion plasma frequency. The dispersion relation has been solved both analytically and numerically. We find that the ratio of the ring speed (u⊥s) to the thermal spread (vts) modifies the dispersion characteristics of the ion-acoustic wave. The contrasting behaviour of the phase velocity of the ion-acoustic wave in the presence of O− ions for u⊥s>vts (and vice versa) can be used to detect the presence of negatively charged oxygen ions and also their thermalization.

Decay Instability of the Ion Acoustic Wave

1975 ◽  
Vol 53 (6) ◽  
pp. 657-665
Author(s):  
S. R. Seshadri
Keyword(s):  
Acoustic Wave ◽  
Acoustic Waves ◽  
Pump Wave ◽  
Plasma Oscillation ◽  
Electron Plasma ◽  
Electromagnetic Mode ◽  
Ion Acoustic Wave ◽  
Plasma Mode ◽  
Ion Plasma ◽  
Ion Acoustic

The parametric excitation of the longitudinal, plasma mode and the transverse, electromagnetic mode in a warm, uniform plasma is investigated for the case in which the pump wave is another electromagnetic mode. The three interacting waves are assumed to propagate in the same direction. The longitudinal mode has two branches, namely, the electron plasma mode and the ion plasma mode. The parametric coupling of the longitudinal and the transverse waves in the presence of the pump wave leads to instabilities of the interacting waves. Illustrative numerical results are presented for the parametric instabilities of the electron plasma oscillation which is a part of the electron plasma mode and those of the ion acoustic waves and the ion plasma oscillations which are parts of the ion plasma mode. The ion acoustic wave is efficiently excited when the pump and the idler wave frequencies are approximately equal to one and a half times the electron plasma frequency.

scholarly journals Effects of Boundary and Electron Inertia on the Ion Acoustic Wave in a Plasma: A Pseudopotential Approach

1998 ◽  
Vol 51 (1) ◽  
pp. 113 ◽  
Author(s):  
K. K. Mondal ◽  
S. N. Paul ◽  
A. Roy Chowdhury
Keyword(s):  
Acoustic Waves ◽  
Finite Geometry ◽  
Cylindrical Domain ◽  
Plasma Parameters ◽  
Ion Acoustic Waves ◽  
Ion Acoustic Wave ◽  
Electron Inertia ◽  
Ion Acoustic ◽  
Pseudopotential Approach ◽  
Range Of Values

A pseudopotential approach is used to analyse the propagation of ion-acoustic waves in a plasma bounded by a cylindrical domain. The effect of the finite geometry is displayed both analytically and numerically. The phase velocity of the wave is determined and its variation is studied with respect to the plasma parameters. It is observed that the pseudopotential shows a wide variation of shape due to the imposition of a finite boundary condition. It is shown that if the other parameters are kept within a certain range of values, then the trapping of particles is favoured when the presence of the boundary is taken into account.

Freestreaming mode excited by a pulse

1986 ◽  
Vol 64 (7) ◽  
pp. 768-772
Author(s):  
Ludwig Schott
Keyword(s):  
Acoustic Waves ◽  
Voltage Pulse ◽  
Velocity Distribution Function ◽  
Density Perturbation ◽  
Zeroth Order ◽  
Ion Acoustic Waves ◽  
Ion Acoustic Wave ◽  
Ion Acoustic ◽  
Analytic Expressions ◽  
Applied Voltage Pulse

When a voltage pulse is applied to an exciter (probe or grid) immersed in a plasma, both an ion-acoustic wave and a freestreaming (ballistic) signal are excited. It is shown that the density perturbation produced by the freestreaming signal is independent of the shape of the applied-voltage pulse for times that are large compared with the temporal width of the pulse and at distances that are large compared with the size of the sheath at the exciter, but it depends on the second derivative of the zeroth-order velocity-distribution function. Analytic expressions that are valid for all times and positions are derived for a simple sheath model. Criteria are presented that enable the experimentalist to distinguish freestreaming modes from ion-acoustic waves.

Nonlinear interaction of slow Alfvén wave with ion acoustic wave and applications to space plasma

2013 ◽  
Vol 79 (5) ◽  
pp. 833-836 ◽  
Author(s):  
B. K. DAS ◽  
R. P. SHARMA ◽  
N. YADAV
Keyword(s):  
Acoustic Waves ◽  
Analytical Study ◽  
Pump Wave ◽  
Modulational Instability ◽  
Solar Wind Plasma ◽  
Alfven Wave ◽  
Ion Acoustic Waves ◽  
Ion Acoustic Wave ◽  
Ion Acoustic ◽  
Model Equations

AbstractThe paper is concerned with the analytical study of nonlinear coupling of slow Alfvén wave (SW) with ion acoustic waves (IAWs) in high-β and low-β plasmas. Here the pump wave (SW) number density gets perturbed in the presence of IAW. The model equations of IAW and SW turn out to be the modified Zakharov system of equations when the ponderomotive nonlinearities are incorporated in the IAW and SW dynamics. Growth rate of modulational instability has been calculated. The relevance of these investigations for solar wind plasma and solar coronal plasma has also been discussed.

Plasma boundary motion and the ion-acoustic wave

1983 ◽  
Vol 30 (1) ◽  
pp. 133-151 ◽  
Author(s):  
N. St. J. Braithwaite ◽  
L. M. Wickens
Keyword(s):  
Acoustic Wave ◽  
Acoustic Waves ◽  
Plasma Boundary ◽  
Planar Geometry ◽  
Wave Form ◽  
Ion Acoustic Wave ◽  
Sheath Edge ◽  
Ion Acoustic ◽  
Characteristics Analysis ◽  
Voltage Wave

Ion-acoustic waves can be launched into plasmas by applying an oscillating voltage wave form to an electrode. The precise mechanism by which these waves are launched from such an electrode is not fully understood. The work described here examines the modelling of sheath edge motion in connexion with acoustic wave launching in both planar and spherical geometries. A novel demonstration of the applicability of the kinetic Bohm criterion is given by using the method of characteristics. A characteristics analysis is also used to show that an expanding, but decelerating, non-planar sheath can give rise to quasi-neutral compression-like features in a plasma. It is also shown that in planar geometry neither this kind of expansion, nor an oscillatory sheath motion, generates compression-like features.

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