scholarly journals The Propagation of Compressional Alfven Waves in Nonuniform Plasmas

1974 ◽  
Vol 27 (2) ◽  
pp. 181 ◽  
Author(s):  
R Morrow ◽  
MH Brennan

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.

1970 ◽  
Vol 25 (1) ◽  
pp. 145-147 ◽  
Author(s):  
H. W. Drawin

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.


2020 ◽  
Vol 86 (6) ◽  
Author(s):  
J. Robertson ◽  
T. A. Carter ◽  
S. Vincena

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.


2006 ◽  
Vol 48 (8) ◽  
pp. 1155-1163 ◽  
Author(s):  
Y Yamaguchi ◽  
M Ichimura ◽  
H Higaki ◽  
S Kakimoto ◽  
K Nakagome ◽  
...  

2007 ◽  
Vol 44 (3) ◽  
pp. 533-536 ◽  
Author(s):  
T. M. Mishonov ◽  
M. V. Stoev ◽  
Y. G. Maneva

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

2019 ◽  
Vol 4 (5) ◽  
Author(s):  
Martin Magill ◽  
Aaron Coutino ◽  
Benjamin A. Storer ◽  
Marek Stastna ◽  
Francis J. Poulin

2000 ◽  
Vol 195 ◽  
pp. 439-441
Author(s):  
D.-Y. Wang ◽  
Y. Ma

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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