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 Physical conditions in H II galaxies

2003 ◽  
Vol 212 ◽  
pp. 722-723
Author(s):  
Carolina Kehrig ◽  
Eduardo Telles ◽  
François Cuisinier
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Statistical Properties ◽  
Chemical Abundances ◽  
Physical Conditions ◽  
Temperature Electron

We present a spectrophotometric survey of 111 H ii galaxies. Observations were made at the ESO 1.52m telescope, with the b&c spectrograph. Our sample presents a great overlap with Terlevich et al. 1991. Additional targets come from the Calan-Tololo an Marseille catalogues. All objects have been observed and analysed homogeneously. We analyse their statistical properties and derive physical conditions (reddening, electron temperature, electron density), as well as chemical abundances.

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.

Hybrid simulation of instabilities in capacitively coupled RF CF4/Ar plasmas

2022 ◽  
Author(s):  
Wan Dong ◽  
Yi Fan Zhang ◽  
ZhongLing Dai ◽  
Julian Schulze ◽  
Yuan-Hong Song ◽  
...  
Keyword(s):  
Electric Field ◽  
Electron Temperature ◽  
Electron Impact ◽  
Electron Density ◽  
Etching Rate ◽  
Reaction Rates ◽  
High Energy ◽  
Density Fluctuations ◽  
Negative Ion ◽  
Capacitively Coupled

Abstract Radio frequency capacitively coupled plasmas (RF CCPs) sustained in fluorocarbon gases or their mixtures with argon are widely used in plasma-enhanced etching. In this work, we conduct studies on instabilities in a capacitive CF4/Ar (1:9) plasma driven at 13.56 MHz at a pressure of 150 mTorr, by using a one-dimensional fluid/Monte-Carlo (MC) hybrid model. Fluctuations are observed in densities and fluxes of charged particles, electric field, as well as electron impact reaction rates, especially in the bulk. As the gap distance between the electrodes increases from 2.8 cm to 3.8 cm, the fluctuation amplitudes become smaller gradually and the instability period gets longer, as the driving power density ranges from 250 to 300 W/m2. The instabilities are on a time scale of 16-20 RF periods, much shorter than those millisecond periodic instabilities observed experimentally owing to attachment/detachment in electronegative plasmas. At smaller electrode gap, a positive feedback to the instability generation is induced by the enhanced bulk electric field in the highly electronegative mode, by which the electron temperature keeps strongly oscillating. Electrons at high energy are mostly consumed by ionization rather than attachment process, making the electron density increase and overshoot to a much higher value. And then, the discharge becomes weakly electronegative and the bulk electric field becomes weak gradually, resulting in the continuous decrease of the electron density as the electron temperature keeps at a much lower mean value. Until the electron density attains its minimum value again, the instability cycle is formed. The ionization of Ar metastables and dissociative attachment of CF4 are noticed to play minor roles compared with the Ar ionization and excitation at this stage in this mixture discharge. The variations of electron outflow from and negative ion inflow to the discharge center need to be taken into account in the electron density fluctuations, apart from the corresponding electron impact reaction rates. We also notice more than 20% change of the Ar+ ion flux to the powered electrode and about 16% difference in the etching rate due to the instabilities in the case of 2.8 cm gap distance, which is worthy of more attention for improvement of etching technology.

Leistungseinkopplung in ein Plasma erhöhter Elektronentemperatur bei der unteren Hybridresonanz

1978 ◽  
Vol 33 (12) ◽  
pp. 1447-1451
Author(s):  
G. Glomski ◽  
B. Heinrich ◽  
H. Schlüter
Keyword(s):  
Electron Temperature ◽  
Electron Density ◽  
Reactive Power ◽  
Transfer Efficiency ◽  
Lower Hybrid ◽  
Power Transfer ◽  
Resonant Coupling

Abstract Previous investigations of lower hybrid resonant coupling to plasmas of low collision frequencies and elevated electron temperature are extended to cover a range of some mW to 1500 W of reactive power. Though resonant behaviour is observed throughout, the efficiency of power transfer is lowered when a threshold at about 1 Watt of reactive power is surpassed. Moreover there is a limited decrease of electron density. For high powers saturation in the drop of transfer efficiency is observed.

scholarly journals Spatial structure of auroral day-time ionospheric electron density irregularities generated by a powerful HF-wave

1998 ◽  
Vol 16 (7) ◽  
pp. 812-820 ◽  
Author(s):  
E. D. Tereshchenko ◽  
B. Z. Khudukon ◽  
M. T. Rietveld ◽  
A. Brekke
Keyword(s):  
Statistical Analysis ◽  
Radio Wave ◽  
Electron Density ◽  
Large Scale ◽  
Density Fluctuations ◽  
Small Scale ◽  
Ionospheric Heating ◽  
Mean Values ◽  
Hf Wave ◽  
Electron Density Irregularities

Abstract. We describe an experiment in satellite radio-wave probing of the ionosphere, modified by powerful waves from the HF heating facility at Tromsø (Norway) in May 1995. Amplitude scintillations and variations of the phase of VHF signals from Russian navigational satellites passing over the heated region were observed. We show that both large-scale electron density irregularities (several tens of kilometers in size) and small-scale ones (from hundreds of meters to kilometers) can be generated by the HF radiation. Maximum effects caused by small-scale irregularities detected in the satellite signals are observed in the directions sector approximately parallel to the geomagnetic field lines although large-scale structures can be detected within a much larger area. The properties of small-scale irregularities (electron density fluctuations) are investigated by applying a statistical analysis and by studying experimental and model mean values of the logarithm of the relative amplitude of the signal. The results indicate that satellite radio probing can be a supporting diagnostic technique for ionospheric heating and add valuable information to studies of effects produced by HF modification.Key words. Satellite radio-wave probing · HF radiation · Electron density irregularities · Statistical analysis · Ionospheric heating

scholarly journals Study by Optical Spectroscopy of Bismuth Emission in a Nanosecond-Pulsed Discharge Created in Liquid Nitrogen

Molecules ◽  
2021 ◽  
Vol 26 (23) ◽  
pp. 7403
Author(s):  
Anna V. Nominé ◽  
Cédric Noel ◽  
Thomas Gries ◽  
Alexandre Nominé ◽  
Valentin A. Milichko ◽  
...  
Keyword(s):  
Electron Temperature ◽  
Liquid Nitrogen ◽  
Electron Density ◽  
Optical Emission ◽  
Time Resolved ◽  
Main Discharge ◽  
Temperature Electron ◽  
Discharge Parameters ◽  
Pulsed Discharges ◽  
Bismuth Electrodes

Time-resolved optical emission spectroscopy of nanosecond-pulsed discharges ignited in liquid nitrogen between two bismuth electrodes is used to determine the main discharge parameters (electron temperature, electron density and optical thickness). Nineteen lines belonging to the Bi I system and seven to the Bi II system could be recorded by directly plunging the optical fibre into the liquid in close vicinity to the discharge. The lack of data for the Stark parameters to evaluate the broadening of the Bi I lines was solved by taking advantage of the time-resolved information supported by each line to determine them. The electron density was found to decrease exponentially from 6.5 ± 1.5 × 1016 cm−3 200 ns after ignition to 1.0 ± 0.5 × 1016 cm−3 after 1050 ns. The electron temperature was found to be 0.35 eV, close to the value given by Saha’s equation.

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