scholarly journals The Propagation of Compressional Alfven Waves in Nonuniform Plasmas

1974 ◽  
Vol 27 (2) ◽  
pp. 181 ◽  
Author(s):  
R Morrow ◽  
MH Brennan
Keyword(s):  
Neutral Particle ◽  
Cyclotron Frequency ◽  
Particle Density ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Theoretical Treatment ◽  
Hydrogen Atoms ◽  
Ion Density ◽  
Total Particle ◽  
Plasma Nonuniformity

A theoretical treatment is presented for the propagation of Alfven waves in a plasma. It includes the effects of resistivity, ion-neutral collisions, the ion cyclotron frequency and radial nonuniformities in ion density, neutral particle density and temperature. The theory is applied to plasmas with conducting and nonconducting walls and the results are compared with those of experiments conducted in the afterglow of a shock-produced plasma. Nonuniformity in the ion density is found to have a marked effect on the dispersion relation and wave field profiles, while non uniformities in the total particle density and temperature are less important. Excellent agreement is obtained between theory and experiment and this allows unambiguous and accurate determinations to be made of the average total particle density, which is found to be - 50 % of the initial filling density, and of the cross section for momentum transfer between protons and hydrogen atoms.

Influence of Atom-Atom Collisions on the Population Densities of Excited Atomic Levels

1970 ◽  
Vol 25 (1) ◽  
pp. 145-147 ◽  
Author(s):  
H. W. Drawin
Keyword(s):  
Thermal Plasma ◽  
Neutral Particle ◽  
Particle Density ◽  
Coupled System ◽  
Rate Equations ◽  
Gas Temperature ◽  
Hydrogen Atoms ◽  
Population Densities ◽  
Non Thermal Plasma ◽  
Quantitative Spectroscopy

Abstract The number densities of excited hydrogen atoms in a non-thermal plasma have been calculated on the basis of a coupled system of rate equations (25 levels) in which one accounts for electron-atom and atom-atom collisions. The calculated population densities depend strongly on the neutral particle density na when ne/na≪1. When the electron temperature, Te, is different from the gas temperature, Tg , the number densities of the excited levels are determined by Tg rather than by Te. This is important in connection with the quantitative spectroscopy of plasmas.

scholarly journals Propagation of shear Alfvén waves in a two-ion plasma and application as a diagnostic for the ion density ratio

2020 ◽  
Vol 86 (6) ◽  
Author(s):  
J. Robertson ◽  
T. A. Carter ◽  
S. Vincena
Keyword(s):  
Density Ratio ◽  
Cutoff Frequency ◽  
Diagnostic Technique ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Larmor Radius ◽  
Alfvén Waves ◽  
Ion Density ◽  
Background Magnetic Field ◽  
Shear Alfven Waves

In this paper, we propose an efficient diagnostic technique for determining spatially resolved measurements of the ion density ratio in a magnetized two-ion species plasma. Shear Alfvén waves were injected into a mixed helium–neon plasma using a magnetic loop antenna, for frequencies spanning the ion cyclotron regime. Two distinct propagation bands are observed, bounded by $\omega < \varOmega _\textrm {Ne}$ and $\omega _{ii} < \omega < \varOmega _\textrm {He}$ , where $\omega _{ii}$ is the ion–ion hybrid cutoff frequency and $\varOmega _\textrm {He}$ and $\varOmega _\textrm {Ne}$ are the helium and neon cyclotron frequencies, respectively. A theoretical analysis of the cutoff frequency was performed and shows it to be largely unaffected by kinetic electron effects and collisionality, although it can deviate significantly from $\omega _{{ii}}$ in the presence of warm ions due to ion finite Larmor radius effects. A new diagnostic technique and accompanying algorithm was developed in which the measured parallel wavenumber $k_\parallel$ is numerically fit to the predicted inertial Alfvén wave dispersion in order to resolve the local ion density ratio. A major advantage of this algorithm is that it only requires a measurement of $k_\parallel$ and the background magnetic field in order to be employed. This diagnostic was tested on the Large Plasma Device at UCLA and was successful in yielding radially localized measurements of the ion density ratio.

Eigenmode formations ofm= 1 fast Alfvén waves in the ion-cyclotron frequency range in the GAMMA 10 central cell

2006 ◽  
Vol 48 (8) ◽  
pp. 1155-1163 ◽  
Author(s):  
Y Yamaguchi ◽  
M Ichimura ◽  
H Higaki ◽  
S Kakimoto ◽  
K Nakagome ◽  
...  
Keyword(s):  
Cyclotron Frequency ◽  
Alfven Waves ◽  
Central Cell ◽  
Alfvén Waves ◽  
Frequency Range ◽  
Ion Cyclotron

scholarly journals On the origin of solar wind. Alfvén waves induced jump of coronal temperature

2007 ◽  
Vol 44 (3) ◽  
pp. 533-536 ◽  
Author(s):  
T. M. Mishonov ◽  
M. V. Stoev ◽  
Y. G. Maneva
Keyword(s):  
Solar Wind ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Coronal Temperature

AMPTE/CCE observations of substorm-associated standing Alfvén waves in the midnight sector

1988 ◽  
Vol 15 (11) ◽  
pp. 1287-1290 ◽  
Author(s):  
K. Takahashi ◽  
S. Kokubun ◽  
T. Sakurai ◽  
R. W. McEntire ◽  
T. A. Potemra ◽  
...  
Keyword(s):  
Alfven Waves ◽  
Alfvén Waves

Dynamics of nonlinear Alfvén waves in the shallow water magnetohydrodynamic equations

2019 ◽  
Vol 4 (5) ◽  
Author(s):  
Martin Magill ◽  
Aaron Coutino ◽  
Benjamin A. Storer ◽  
Marek Stastna ◽  
Francis J. Poulin
Keyword(s):  
Shallow Water ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Magnetohydrodynamic Equations

scholarly journals Reacceleration of Relativistic Electrons by Turbulent Alfvén Waves in Radio Jets

2000 ◽  
Vol 195 ◽  
pp. 439-441
Author(s):  
D.-Y. Wang ◽  
Y. Ma
Keyword(s):  
Electron Energy ◽  
Power Law ◽  
Diffusion Approximation ◽  
Alfven Waves ◽  
Alfvén Waves ◽  
Relativistic Electrons ◽  
Radio Jets

Relativistic electrons may be effectively accelerated by turbulent Alfvén waves in radio jets. The acceleration spectrum is a power law with the electron energy as high as γ ~ 106, but the spectrum index is ~ 1.2 in the condition of diffusion approximation, which is less than the observation value.

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