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.

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.

Effect of ion temperature on ion-acoustic solitary waves in a two-ion plasma

1988 ◽  
Vol 66 (6) ◽  
pp. 467-470 ◽  
Author(s):  
Sikha Bhattacharyya ◽  
R. K. Roychoudhury
Keyword(s):  
Mach Number ◽  
Analytical Solution ◽  
Solitary Waves ◽  
Experimental Result ◽  
Ion Temperature ◽  
Ion Plasma ◽  
Ion Acoustic Solitary Waves ◽  
Ion Acoustic ◽  
Cold Ions ◽  
Pseudopotential Approach

The effect of ion temperature on ion-acoustic solitary waves in the case of a two-ion plasma has been investigated using the pseudopotential approach of Sagdeev. An analytical solution for relatively small amplitudes has also been obtained. Our result has been compared, whenever possible, with the experimental result obtained by Nakamura. It is found that a finite ion temperature considerably modifies the restrictions on the Mach number obtained for cold ions.

scholarly journals Dependence on ion temperature of shallow-angle magnetic presheaths with adiabatic electrons

2019 ◽  
Vol 85 (6) ◽  
Author(s):  
Alessandro Geraldini ◽  
F. I. Parra ◽  
F. Militello
Keyword(s):  
Magnetic Field ◽  
Fluid Model ◽  
Boltzmann Distribution ◽  
Distribution Functions ◽  
Magnetized Plasma ◽  
Electron Mass ◽  
Ion Temperature ◽  
Ion Distribution ◽  
Ionic Charge ◽  
The Magnetic Field

The magnetic presheath is a boundary layer occurring when magnetized plasma is in contact with a wall and the angle $\unicode[STIX]{x1D6FC}$ between the wall and the magnetic field $\boldsymbol{B}$ is oblique. Here, we consider the fusion-relevant case of a shallow-angle, $\unicode[STIX]{x1D6FC}\ll 1$ , electron-repelling sheath, with the electron density given by a Boltzmann distribution, valid for $\unicode[STIX]{x1D6FC}/\sqrt{\unicode[STIX]{x1D70F}+1}\gg \sqrt{m_{\text{e}}/m_{\text{i}}}$ , where $m_{\text{e}}$ is the electron mass, $m_{\text{i}}$ is the ion mass, $\unicode[STIX]{x1D70F}=T_{\text{i}}/ZT_{\text{e}}$ , $T_{\text{e}}$ is the electron temperature, $T_{\text{i}}$ is the ion temperature and $Z$ is the ionic charge state. The thickness of the magnetic presheath is of the order of a few ion sound Larmor radii $\unicode[STIX]{x1D70C}_{\text{s}}=\sqrt{m_{\text{i}}(ZT_{\text{e}}+T_{\text{i}})}/ZeB$ , where e is the proton charge and $B=|\boldsymbol{B}|$ is the magnitude of the magnetic field. We study the dependence on $\unicode[STIX]{x1D70F}$ of the electrostatic potential and ion distribution function in the magnetic presheath by using a set of prescribed ion distribution functions at the magnetic presheath entrance, parameterized by $\unicode[STIX]{x1D70F}$ . The kinetic model is shown to be asymptotically equivalent to Chodura’s fluid model at small ion temperature, $\unicode[STIX]{x1D70F}\ll 1$ , for $|\text{ln}\,\unicode[STIX]{x1D6FC}|>3|\text{ln}\,\unicode[STIX]{x1D70F}|\gg 1$ . In this limit, despite the fact that fluid equations give a reasonable approximation to the potential, ion gyro-orbits acquire a spatial extent that occupies a large portion of the magnetic presheath. At large ion temperature, $\unicode[STIX]{x1D70F}\gg 1$ , relevant because $T_{\text{i}}$ is measured to be a few times larger than $T_{\text{e}}$ near divertor targets of fusion devices, ions reach the Debye sheath entrance (and subsequently the wall) at a shallow angle whose size is given by $\sqrt{\unicode[STIX]{x1D6FC}}$ or $1/\sqrt{\unicode[STIX]{x1D70F}}$ , depending on which is largest.

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.

The frequency and damping of ion-acoustic waves

1980 ◽  
Vol 58 (4) ◽  
pp. 565-568 ◽  
Author(s):  
A. J. Barnard ◽  
C. Gulizia
Keyword(s):  
Dispersion Relation ◽  
Electron Temperature ◽  
Acoustic Waves ◽  
Ion Temperature ◽  
Ion Acoustic Waves ◽  
Ion Acoustic

The dispersion relation for a plasma with different ion and electron temperatures is solved numerically to obtain the frequency and the damping constant for ion-acoustic waves as a function of the wavenumber. It is shown that the commonly used expressions for these variables only apply if the parameter T = ziTe/Ti is larger than 20, and can lead to large errors if T is close to 1. (Here z1 is the ion charge, Te is the electron temperature, and Ti the ion temperature.) Tables and graphs of the frequency and damping as functions of the wavenumber are given for different values of T.

A steady-state model of current filamentation caused by the electrothermal instability in a fully ionized magnetized plasma

1982 ◽  
Vol 27 (3) ◽  
pp. 427-435 ◽  
Author(s):  
M. G. Haines ◽  
F. Marsh
Keyword(s):  
Magnetic Field ◽  
Steady State ◽  
Ohmic Heating ◽  
Maximum Growth ◽  
Energy Balance Equation ◽  
Critical Value ◽  
Magnetized Plasma ◽  
Larmor Radius ◽  
Ion Temperature ◽  
Acoustic Instabilities

A magnetically confined two-fluid plasma is considered in which the Ohmic heating of the electrons by a current driven parallel to an applied magnetic field is balanced by bremsstrahlung and equipartition to the ions. It is found that for a steady state the applied electric field must be below a critical value which in absence of bremsstrahlung is given by where the electrical conductivity is and the total pressure is p. Under this condition it is found that there are two /Futions for Te/Ti which satisfy the steady electron energy balance equation in a homogeneous, fully ionized plasma. One of these /Futions always has values above the critical value of Te/Ti (= 132 in absence of bremsstrahlung) for the onset of the electrothermal instability in a fully ionized gas. Inclusion of electron thermal conduction transverse to the magnetic field (with Hall parameter ) yields a wavelength for maximum growth of the instability of about , where ae is the electron Larmor radius. The steady non linear profiles showing current filamentation have been calculated. Runaway electrons and ion-acoustic instabilities can occur in the spatial maximum of the current density and electron temperature. Inclusion of bremsstrahlung loss reduces the value of Te/Ti for the onset of the instability, and at Te = Ti yields a maximum ion temperature obtainable by Ohmic heating in a stable plasma.

Nonlinear modulation of ion-acoustic waves in two-electron-temperature plasmas

2010 ◽  
Vol 76 (2) ◽  
pp. 169-181 ◽  
Author(s):  
A. ESFANDYARI-KALEJAHI ◽  
I. KOURAKIS ◽  
M. AKBARI-MOGHANJOUGHI
Keyword(s):  
Electron Temperature ◽  
Acoustic Waves ◽  
Modulational Instability ◽  
Perturbation Technique ◽  
Density Ratio ◽  
Cold Electron ◽  
Ion Temperature ◽  
Ion Acoustic Waves ◽  
Ion Acoustic ◽  
Nonlinear Modulation

AbstractThe amplitude modulation of ion-acoustic waves is investigated in a plasma consisting of adiabatic warm ions, and two different populations of thermal electrons at different temperatures. The fluid equations are reduced to nonlinear Schrödinger equation by employing a multi-scale perturbation technique. A linear stability analysis for the wave packet amplitude reveals that long wavelengths are always stable, while modulational instability sets in for shorter wavelengths. It is shown that increasing the value of the hot-to-cold electron temperature ratio (μ), for a given value of the hot-to-cold electron density ratio (ν), favors instability. The role of the ion temperature is also discussed. In the limiting case ν = 0 (or ν → ∞), which correspond(s) to an ordinary (single) electron-ion plasma, the results of previous works are recovered.

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