Effective coffision frequency and electron temperature in a weakly ionized argon plasma

1980 ◽  
Vol 23 (2) ◽  
pp. 271-282
Author(s):  
C. P. Schneider
Keyword(s):  
Electron Temperature ◽  
High Frequency ◽  
Collision Frequency ◽  
Argon Plasma ◽  
Angular Frequency ◽  
Weak Electric Field ◽  
Hard Sphere Model ◽  
Plasma Conductivity ◽  
Gas Plasma ◽  
Weakly Ionized

Herein is described a calculation of the effective coffision frequency νeffof a low- density, shock-heated argon plasma under the influence of a weak electric field which oscillates harmonically with angular frequency ω. It is shown that, for the high frequency case ω >whereis the collision frequency in a Maxwellian gas plasma, one has νeff⋍ 2, provided that the imaginary part of the argon plasma conductivity is negligibly small in comparison to the real part. The influence of the theoretical model used to calculate νeffon the values of the electron temperatureTederived from measurements is compared with the results obtained in a data reduction for which the hard-sphere model for particle encounters was utilized.

Scattering of electromagnetic waves by hybrid waves in a two-electron-temperature plasma

1991 ◽  
Vol 46 (1) ◽  
pp. 99-106 ◽  
Author(s):  
S. K. Sharma ◽  
A. Sudarshan
Keyword(s):  
Growth Rate ◽  
Electron Temperature ◽  
High Frequency ◽  
Electromagnetic Waves ◽  
Low Frequency ◽  
Lower Hybrid ◽  
Stimulated Scattering ◽  
Coupled Modes ◽  
Temperature Plasma ◽  
Electrostatic Perturbation

In this paper, we use the hydrodynamic approach to study the stimulated scattering of high-frequency electromagnetic waves by a low-frequency electrostatic perturbation that is either an upper- or lower-hybrid wave in a two-electron-temperature plasma. Considering the four-wave interaction between a strong high-frequency pump and the low-frequency electrostatic perturbation (LHW or UHW), we obtain the dispersion relation for the scattered wave, which is then solved to obtain an explicit expression for the growth rate of the coupled modes. For a typical Q-machine plasma, results show that in both cases the growth rate increases with noh/noc. This is in contrast with the results of Guha & Asthana (1989), who predicted that, for scattering by a UHW perturbation, the growth rate should decrease with increasing noh/noc.

scholarly journals Variation in altitude of high-frequency enhanced plasma line by the pump near the 5th electron gyro-harmonic

2019 ◽  
Author(s):  
Jun Wu ◽  
Jian Wu ◽  
Michael T. Rietveld ◽  
Ingemar Haggstrom ◽  
Haisheng Zhao ◽  
...  
Keyword(s):  
Electron Temperature ◽  
High Frequency ◽  
Langmuir Wave ◽  
Decisive Role ◽  
Bragg Condition ◽  
Pump Frequency ◽  
Ionospheric Heating ◽  
Lower Altitude ◽  
Incoherent Scatter ◽  
Plasma Line

Abstract. During an ionospheric heating campaign carried out at the European Incoherent Scatter Scientific Association (EISCAT), the ultra high frequency incoherent scatter (IS) radar observed a systematic variation in the altitude of the high-frequency enhanced plasma line (HFPL), which behaves depending on the pump frequency. Specifically, the HFPL altitude becomes lower when the pump lies above the 5th gyro-harmonic. The analysis shows that the enhanced electron temperature plays a decisive role in the descent in the HFPL altitude. That is, on the traveling path of the enhanced Langmuir wave, the enhanced electron temperature can only be matched by the low electron density at a lower altitude so that the Bragg condition can be satisfied, as expected from the dispersion relation of Langmuir wave.

DIFFERENCE FREQUENCY HARMONIC ION HEATING

1967 ◽  
Vol 45 (5) ◽  
pp. 1771-1781 ◽  
Author(s):  
C. R. James ◽  
W. B. Thompson
Keyword(s):  
High Frequency ◽  
Collision Frequency ◽  
Difference Frequency ◽  
Fourth Power ◽  
Heating Process ◽  
Ion Heating ◽  
Frequency Signal ◽  
Transverse Waves ◽  
The Difference ◽  
Frequency Harmonic

The heating of a magnetized hot diffuse plasma using the difference frequency signal generated from two high-frequency (35 GHz) transverse waves is examined. The plasma is described by the cold plasma model and a series expansion of harmonics is used to obtain a solution to the equations. It is shown that the energy absorbed by the ions can be made inversely proportional to the collision frequency and the fourth power of the driven frequency and proportional to the fourth power of the driven electric field intensity. An investigation of the sensitivity of the heating process to fluctuations in frequency, density, and d-c. magnetic field is carried out.

New low-frequency waves and negative mass instability in dusty plasmas

2010 ◽  
Vol 76 (6) ◽  
pp. 929-937
Author(s):  
D. P. RESENDES ◽  
R. BINGHAM ◽  
S. MOTA ◽  
V. N. TSYTOVICH
Keyword(s):  
Electron Temperature ◽  
Free Path ◽  
Collision Frequency ◽  
Low Frequency ◽  
Mean Free Path ◽  
Sound Waves ◽  
Ion Temperature ◽  
Plasma Particle ◽  
Charging Mode ◽  
Dust Charging

AbstractLow-frequency dusty plasma waves with frequencies much smaller than the frequency of charging collisions of plasma particles with dust particles are considered taking into account elastic and charging collisions of plasma particles with dust and neutrals. The usual dust sound waves with an upper frequency equal to the dust plasma frequency are found to be present only for wavelengths much smaller than the plasma particle effective mean free path due to the effective collision frequency. The effectice collision frequency is found to be inversely proportional to the square root of the product of the charging frequency and the frequency of particle momentum losses, involving processes due to elastic plasma particle–dust collisions and collisions with neutrals. It is shown that when the wavelength of the wave is much larger than the mean free path for effective collisions, the properties of the waves are different from those considered previously. A negative mass instability is found in this domain of frequencies when the effective mean free path of ions is larger than the effective mean free path of electrons. In the absence of neutrals, this appears to be possible only if the temperature of ions exceeds the electron temperature. This can occur in laboratory experiments and space plasmas but not in plasma-etching experiments. In the absence of instability, a new dust oscillation, a dust charging mode, is found, whose frequency is almost constant over a certain range of wave numbers. It is inversely proportional to the dust mass and charging frequency of the dust. A new dust electron sound wave is found for frequencies less than the frequency of the dust charging mode. The velocity of the dust electron sound wave is determined by the electron temperature but not the ion temperature, as for the usual dust sound waves, with the electron temperature substantially exceeding the ion temperature.

scholarly journals Numerical study of the generation and propagation of ultralow-frequency waves by artificial ionospheric F region modulation at different latitudes

2016 ◽  
Vol 34 (9) ◽  
pp. 815-829
Author(s):  
Xiang Xu ◽  
Chen Zhou ◽  
Run Shi ◽  
Binbin Ni ◽  
Zhengyu Zhao ◽  
...  
Keyword(s):  
Electron Temperature ◽  
High Frequency ◽  
Ring Current ◽  
Modulation Frequency ◽  
Current Source ◽  
Temperature Oscillation ◽  
Ulf Waves ◽  
Ultralow Frequency ◽  
Ulf Wave ◽  
F Region

Abstract. Powerful high-frequency (HF) radio waves can be used to efficiently modify the upper-ionospheric plasmas of the F region. The pressure gradient induced by modulated electron heating at ultralow-frequency (ULF) drives a local oscillating diamagnetic ring current source perpendicular to the ambient magnetic field, which can act as an antenna radiating ULF waves. In this paper, utilizing the HF heating model and the model of ULF wave generation and propagation, we investigate the effects of both the background ionospheric profiles at different latitudes in the daytime and nighttime ionosphere and the modulation frequency on the process of the HF modulated heating and the subsequent generation and propagation of artificial ULF waves. Firstly, based on a relation among the radiation efficiency of the ring current source, the size of the spatial distribution of the modulated electron temperature and the wavelength of ULF waves, we discuss the possibility of the effects of the background ionospheric parameters and the modulation frequency. Then the numerical simulations with both models are performed to demonstrate the prediction. Six different background parameters are used in the simulation, and they are from the International Reference Ionosphere (IRI-2012) model and the neutral atmosphere model (NRLMSISE-00), including the High Frequency Active Auroral Research Program (HAARP; 62.39° N, 145.15° W), Wuhan (30.52° N, 114.32° E) and Jicamarca (11.95° S, 76.87° W) at 02:00 and 14:00 LT. A modulation frequency sweep is also used in the simulation. Finally, by analyzing the numerical results, we come to the following conclusions: in the nighttime ionosphere, the size of the spatial distribution of the modulated electron temperature and the ground magnitude of the magnetic field of ULF wave are larger, while the propagation loss due to Joule heating is smaller compared to the daytime ionosphere; the amplitude of the electron temperature oscillation decreases with latitude in the daytime ionosphere, while it increases with latitude in the nighttime ionosphere; both the electron temperature oscillation amplitude and the ground ULF wave magnitude decreases as the modulation frequency increases; when the electron temperature oscillation is fixed as input, the radiation efficiency of the ring current source is higher in the nighttime ionosphere than in the daytime ionosphere.

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