Stabilization of lower hybrid drift modes by finite parallel wavenumber and electron temperature gradients in field‐reversed configurations

1989 ◽  
Vol 1 (8) ◽  
pp. 1654-1658 ◽  
Author(s):  
R. Farengo ◽  
P. N. Guzdar ◽  
Y. C. Lee
Keyword(s):  
Electron Temperature ◽  
Temperature Gradients ◽  
Lower Hybrid ◽  
Electron Temperature Gradients ◽  
Field Reversed Configurations

scholarly journals The Chemical Features of Galactic Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 575-575
Author(s):  
P. R. Amnuel
Keyword(s):  
Chemical Composition ◽  
Electron Temperature ◽  
Planetary Nebulae ◽  
Temperature Gradients ◽  
Element Abundances ◽  
Electron Temperature Gradients ◽  
The Masses ◽  
Progenitor Stars

The chemical composition of 218 galactic planatary nebulae is investigated, all the nebulae are divided into four classes according to the masses of the nebulae and progenitor stars. The values of local abundances, galactic abundances and electron temperature gradients are found for each class of nebulae. The correlations between element abundances are also investigated. The results are compared with theorical predictions.

scholarly journals Enhanced ion acoustic fluctuations and ion outflows

1999 ◽  
Vol 17 (2) ◽  
pp. 182-189 ◽  
Author(s):  
F. R. E. Forme ◽  
D. Fontaine
Keyword(s):  
Electron Temperature ◽  
Temperature Gradients ◽  
Spectral Signature ◽  
Simultaneous Occurrence ◽  
Plasma Parameters ◽  
Strong Electron ◽  
Ion Drift ◽  
Incoherent Scatter ◽  
Ion Acoustic ◽  
Electron Temperature Gradients

Abstract. A number of observations showing enhanced ion acoustic echoes observed by means of incoherent scatter radars have been reported in the literature. The received power is extremely enhanced by up to 1 or 2 orders of magnitude above usual values, and it is mostly contained in one of the two ion acoustic lines. This spectral asymmetry and the intensity of the received signal cannot be resolved by the standard analysis procedure and often causes its failure. As a result, and in spite of a very clear spectral signature, the analysis is unable to fit the plasma parameters inside the regions of ion acoustic turbulence. We present European Incoherent Scatter radar (EISCAT) observations of large ion outflows associated with the simultaneous occurrence of enhanced ion acoustic echoes. The ion fluxes can reach 1014 m-2 s-1 at 800 km altitude. From the very clear spectral signatures of these echoes, a method is presented to extract estimates of the electron temperature and the ion drift within the turbulent regions. It is shown that the electron gas is strongly heated up to 11 000 K. Also electron temperature gradients of about 0.02 K/m exist. Finally, the estimates of the electron temperature and of the ion drift are used to study the possible implications for the plasma transport inside turbulent regions. It is shown that strong electron temperature gradients cause enhancement of the ambipolar electric field and can account for the observed ion outflows.Key words. Ionosphere (auroral ionosphere; ionosphere · magnetosphere interactions; plasma waves and instabilities).

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.

Spectroscopic Measurement of Electron Temperature during Lower Hybrid Current Startup in JIPP T-IIU Tokamak

1986 ◽  
Vol 25 (Part 1, No. 3) ◽  
pp. 458-463 ◽  
Author(s):  
Mikio Mimura ◽  
Kuninori Sato ◽  
Kazuo Toi ◽  
Junji Fujita
Keyword(s):  
Electron Temperature ◽  
Spectroscopic Measurement ◽  
Lower Hybrid

scholarly journals Analysis of Observations near the Fourth Electron Gyrofrequency Heating Experiment in EISCAT

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 191
Author(s):  
Zeyun Li ◽  
Hanxian Fang ◽  
Hongwei Gong ◽  
Zhe Guo
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Parametric Instability ◽  
Density Fluctuations ◽  
Lower Hybrid ◽  
Langmuir Waves ◽  
Ionospheric Heating ◽  
Superthermal Electron ◽  
Temperature Electron ◽  
Electron Gyrofrequency

We present the observations of the artificial ionospheric heating experiment of EISCAT (European Incoherent Scatter Scientific Association) on 22 February 2012 in Tromsø, Norway. When the pump is operating near the fourth electron gyrofrequency, the UHF radar observation shows some strong enhancements in electron temperature, electron density, ion line, and the outshifted plasma lines. Based on some existing theories, we find the following: first, Langmuir waves scattering off lower hybrid density fluctuations and strong Langmuir turbulence (SLT) in the Zakharov model cannot completely explain the outshifted plasma lines, but the data suggest that this phenomenon is related to the cascade of the pump wave and should be researched further; second, the spatiotemporal consistency between the enhancement in electron density/electron temperature reaches up to three to four times that of the undisturbed state and HF-enhanced ion lines (HFILs) suggest that SLT excited by parametric instability plays a significant role in superthermal electron formation and electron acceleration; third, some enhancements in HFILs and HF-induced plasma lines (HFPLs) are generated by parametric decay instability (PDI) during underdense heating in the third cycle, we suggest that this is due to the existence of a second cut-off in the upper hybrid dispersion relation as derived from a kinetic description.

scholarly journals Nichtlineare Welleneinkopplung in ein Plasma erhöhter Elektronentemperatur / Nonlinear Wave Coupling to a Plasma of Enhanced Electron Temperature

1976 ◽  
Vol 31 (12) ◽  
pp. 1566-1571 ◽  
Author(s):  
G. Glomski ◽  
B. Heinrich ◽  
H. Schlüter
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Nonlinear Wave ◽  
Lower Hybrid ◽  
Radio Waves ◽  
Wave Coupling ◽  
Neutral Gas ◽  
At Resonance ◽  
Parametric Effects ◽  
Lower Hybrid Resonance

Abstract Nonlinear Wave Coupling to a Plasma of Enhanced Electron Temperature In continuation of former investigations radio waves of different amplitude in the domain of lower hybrid resonance were coupled to a plasma of enhanced electron temperature. Under linear conditions no dependence of resonance behaviour on the wave amplitude was observed. Exceeding a treshhold maximum of absorption and electron density decreased significantly; both observations may be explained by onset of nonlinear and parametric effects. Increasing the amplitude the discharge only could be maintained by increasing the neutral gas pressure. In the power range of 15 to 20 kW electron density grew rapidly at resonance.

Quasimode decay of a lower-hybrid wave in a two-electron-temperature plasma

1996 ◽  
Vol 56 (2) ◽  
pp. 237-249
Author(s):  
A. Sudarshan ◽  
S. K. Sharma
Keyword(s):  
Growth Rate ◽  
Electron Temperature ◽  
Decay Channel ◽  
Lower Hybrid ◽  
Hybrid Wave ◽  
Lower Hybrid Wave ◽  
Temperature Plasma ◽  
Parametric Decay ◽  
Cylindrical Plasma ◽  
Ion Cyclotron

We study the quasimode decay of a lower-hybrid wave and a damped ion cyclotron wave in a plasma having two kinds of electrons. This decay channel is also investigated for a cylindrical plasma. The behaviour of the threshold and growth rate with variations in Tn/Tc and non/noc are studied, and a comparison is made with previous results. Our results show that the growth rate and the threshold for the onset of parametric decay are influenced by the presence of the second electron species.

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