Excitation of upper-hybrid waves by a thermal parametric instability

1983 ◽  
Vol 30 (3) ◽  
pp. 463-478 ◽  
Author(s):  
M. C. Lee ◽  
S. P. Kuo
Keyword(s):  
Ohmic Heating ◽  
Parametric Instability ◽  
Wave Interaction ◽  
Present Theory ◽  
Magnetized Plasma ◽  
Coupling Mechanism ◽  
Ionospheric Heating ◽  
Plasma Line ◽  
Thermal Parametric Instability ◽  
Hybrid Waves

A purely growing instability characterized by a four-wave interaction has been analysed in a uniform, magnetized plasma. Up-shifted and down-shifted upper-hybrid waves and a non-oscillatory mode can be excited by a pump wave of ordinary rather than extraordinary polarization in the case of ionospheric heating. The differential Ohmic heating force dominates over the ponderomotive force as the wave–wave coupling mechanism. The beating current at zero frequency produces a significant stabilizing effect on the excitation of short-scale modes by counterbalancing the destabilizing effect of the differential Ohmic heating. The effect of ionospheric inhomogeneity is estimated, showing a tendency to raise the thresholds of the instability. When applied to ionospheric heating experiments, the present theory can explain the excitation of field-aligned plasma lines and ionospheric irregularities with a continuous spectrum ranging from metre-scale to hundreds of metre-scale. Further, the proposed mechanism may become a competitive process to the parametric decay instability and be responsible for the overshoot phenomena of the plasma line enhancement at Arecibo.

Theory of magnetosonic wave—plateau shocks driven by upper-hybrid waves

1990 ◽  
Vol 44 (3) ◽  
pp. 489-506 ◽  
Author(s):  
N. N. Rao
Keyword(s):  
Wave Structure ◽  
Present Theory ◽  
Finite Amplitude ◽  
Magnetized Plasma ◽  
Magnetosonic Wave ◽  
Number Density ◽  
Dense Structure ◽  
Hybrid Waves ◽  
The Magnetic Field ◽  
Front Region

The existence as well as the structure of magnetosonic wave-plateau shocks driven by upper-hybrid waves in a two-component electron-ion magnetized plasma is analysed. In the incident region the field quantities have a standing-wave structure, whereas in the evanescent region they monotonically reach constant values. The plasma flow velocity undergoes a transition from submagnetosonic (in the evanescent region) to supermagnetosonic (in the incident region) values via the magnetosonic point. The number density (or the magnetic field) across the shock-front region has a steep gradient and connects a rarefaction (under-dense) wave in the incident region to a shelf-like (over-dense) structure in the evanescent region, where the upper-hybrid electric field drops to zero monotonically. For the case of small- but finite-amplitude shocks the detailed structures of the profiles are obtained analytically. For large-amplitude shocks the profiles are computed using numerical methods. An extension of the present theory as well as some possible applications are pointed out.

scholarly journals Resonant three-wave interaction in the presence of suprathermal electron fluxes

2004 ◽  
Vol 22 (6) ◽  
pp. 2171-2179 ◽  
Author(s):  
C. Krafft ◽  
A. Volokitin
Keyword(s):  
Electron Distribution Function ◽  
Wave Interaction ◽  
Magnetized Plasma ◽  
Lower Hybrid ◽  
Particle Interactions ◽  
Wave Interactions ◽  
Suprathermal Electron ◽  
Hybrid Waves ◽  
The Waves ◽  
Lower Hybrid Waves

Abstract. A theoretical and numerical model is presented which describes the nonlinear interaction of lower hybrid waves with a non-equilibrium electron distribution function in a magnetized plasma. The paper presents some relevant examples of numerical simulations which show the nonlinear evolution of a set of three waves interacting at various resonance velocities with a flux of electrons presenting some anisotropy in the parallel velocity distribution (suprathermal tail); in particular, the case when the interactions between the waves are neglected (for sufficiently small waves' amplitudes) is compared to the case when the three waves follow a resonant decay process. A competition between excitation (due to the fan instability with tail electrons or to the bump-in-tail instability at the Landau resonances) and damping processes (involving bulk electrons at the Landau resonances) takes place for each wave, depending on the strength of the wave-wave coupling, on the linear growth rates of the waves and on the modifications of the particles' distribution resulting from the linear and nonlinear wave-particle interactions. It is shown that the energy carried by the suprathermal electron tail is more effectively transfered to lower energy electrons in the presence of wave-wave interactions.

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.

scholarly journals Predicted and observed characteristics of small-scale field-aligned irregularities generated in the F-region by low power HF heating

2002 ◽  
Vol 20 (5) ◽  
pp. 647-653 ◽  
Author(s):  
E. Kolesnikova ◽  
T. R. Robinson ◽  
J. A. Davies
Keyword(s):  
Low Power ◽  
Decay Rate ◽  
Parametric Instability ◽  
Small Scale ◽  
F Region ◽  
Scale Field ◽  
Thermal Parametric Instability ◽  
Hf Heating ◽  
Heated Volume ◽  
Field Aligned Irregularities

Abstract. Simultaneous HF scattering from the different regions of the heated volume is used to investigate characteristics of the small-scale field-aligned irregularities in the F-region. Time of growth, decay rate and saturation level for different pump powers are deduced from the observations and are compared with their behaviour predicted by the thermal parametric instability model. As a result, the estimates of the density and of the temperature modifications inside of the irregularities are obtained.Key words. Ionosphere (ionospheric irregularities)

On reflexion and trapping of upper-hybrid waves

1983 ◽  
Vol 29 (2) ◽  
pp. 195-215 ◽  
Author(s):  
Einar Mjølhus
Keyword(s):  
Magnetic Field ◽  
Singular Perturbation ◽  
Radio Wave ◽  
Perturbation Technique ◽  
Magnetized Plasma ◽  
Small Scale ◽  
Hybrid Wave ◽  
Singular Perturbation Technique ◽  
Hybrid Waves ◽  
Electron Density Irregularities

The theme of the paper is the relation between the so-called Z mode and the upper-hybrid wave in a magnetized plasma. First, certain problems as to reflexion and transmission of upper-hybrid waves at quasi cut-off (that is, cut-off predicted within electrostatic approximation) are stated and solved by singular perturbation technique. Then the theory is extended to a problem concerning generation and trapping of upper-hybrid waves in magnetic field aligned electron density irregularities. First a single density depression is considered, and then the formalism is further extended to a system of many parallel density depressions. The study was motivated by problems in the theory of artificial small-scale ionospheric irregularities occurring in radio wave experiments.

scholarly journals Computer simulations for direct conversion of the HF electromagnetic wave into the upper hybrid wave in ionospheric heating experiments

1998 ◽  
Vol 16 (10) ◽  
pp. 1251-1258 ◽  
Author(s):  
H. O. Ueda ◽  
Y. Omura ◽  
H. Matsumoto
Keyword(s):  
Pump Wave ◽  
Maximum Amplitude ◽  
Direct Conversion ◽  
Conversion Process ◽  
Small Scale ◽  
Ionospheric Heating ◽  
Particle In Cell ◽  
Electromagnetic Pump ◽  
Excited Wave ◽  
Hybrid Waves

Abstract. Excitation of upper hybrid waves associated with the ionospheric heating experiments is assumed to be essential in explaining some of the features of stimulated electromagnetic emissions (SEE). A direct conversion process is proposed as an excitation mechanism of the upper hybrid waves where the energy of an obliquely propagating electromagnetic pump wave is converted into the electrostatic upper hybrid waves due to small-scale density irregularities. We performed electromagnetic particle-in-cell simulations to investigate the energy conversion process in the ionospheric heating experiments. We studied dependence of the amplitude of the excited wave on the propagation angle of the pump wave, scale length of the density irregularity, degree of the irregularity, and thermal velocity of the plasma. The maximum amplitude is found to be 37 of the pump amplitude under an optimum condition.Key words. Ionosphere (ionospheric irregularities; plasma waves and instabilities; wave-particle interactions).

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.

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