scholarly journals Lightning-induced lower-hybrid turbulence and trapped Extremely Low Frequency (ELF) electromagnetic waves observed in deep equatorial plasma density depletions during intense magnetic storms

2008 ◽  
Vol 113 (A11) ◽  
pp. n/a-n/a ◽  
Author(s):  
M. Malingre ◽  
J.-J. Berthelier ◽  
R. Pfaff ◽  
J. Jasperse ◽  
M. Parrot
Keyword(s):  
Plasma Density ◽  
Electromagnetic Waves ◽  
Low Frequency ◽  
Magnetic Storms ◽  
Lower Hybrid ◽  
Extremely Low Frequency

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.

Study of a TGF associated with an Elve using extremely low frequency electromagnetic waves

2020 ◽  
Author(s):  
Volodymyr Marchenko ◽  
Janusz Mlynarczyk ◽  
Michał Ostrowski ◽  
Andrzej Kulak ◽  
Olesia Senchenko ◽  
...  
Keyword(s):  
Electromagnetic Waves ◽  
Low Frequency ◽  
Extremely Low Frequency

scholarly journals Space-time evolution of electron-beam driven electron holes and their effects on the plasma

2003 ◽  
Vol 10 (1/2) ◽  
pp. 53-63 ◽  
Author(s):  
N. Singh
Keyword(s):  
Electron Beam ◽  
Plasma Density ◽  
Three Dimensional ◽  
Low Frequency ◽  
Velocity Distribution Function ◽  
Lower Hybrid ◽  
Particle In Cell ◽  
Short Transverse ◽  
Electron Holes ◽  
Number Of Electron Holes

Abstract. We report here further results from the three-dimensional particle-in-cell simulations of the electron-beam driven electron holes. We focus here on (i) the transformation of oscillatory waves driven by the electron-beam instability into electron holes, (ii) the continued evolution and propagation of electron holes after their formation, including merging of electron holes, and (iii) the effects of the evolution on the plasma density and ion velocity distribution function. We find that initially electron-beam modes with perpendicular wave numbers k^ = 0 and as well as k^ ≠ 0 are driven resonantly below the electron plasma frequency of the target plasma. The modes interact nonlinearly and modulate each other both in space and time, producing wave structures with finite perpendicular scale lengths. Nonlinear evolution of such wave structures generates the electron holes in the simulations. Initially, a large number of electron holes form in the plasma. Their merging yields continuously a decreasing number of electron holes. The propagation velocity of the electron holes evolves dynamically and is affected by their merging. At late times only a few electron holes are left in the simulation and they decay by emitting low-frequency electrostatic whistler waves just above the lower hybrid (LH) frequency vlh . These waves, which are long structures parallel to the ambient magnetic field B0 and quite short transverse to B0, are associated with similar structures in the plasma density, producing density filaments. It turns out that electron-beam driven plasmas, in general, develop such filaments at some stage of the evolution of the beam-driven waves. In view of the excitation of the LH waves near vlh, which could resonate with the ions, an analysis shows that it is possible to heat transversely the ions in a time scale of a few seconds in the auroral return current plasma, in which electron holes and transversely heated ions have been simultaneously observed.

Nonlinear transient signal propagation in homogeneous plasma

1982 ◽  
Vol 28 (1) ◽  
pp. 159-175 ◽  
Author(s):  
D. Jovanović ◽  
H. L. Pécseli ◽  
K. Thomsen
Keyword(s):  
Electromagnetic Waves ◽  
Second Harmonic ◽  
Low Frequency ◽  
Signal Propagation ◽  
Transient Signal ◽  
Lower Hybrid ◽  
Homogeneous Plasma ◽  
Natural Modes ◽  
Nonlinear Transient ◽  
Hybrid Waves

The nonlinear transient evolution of a suddenly applied monochromatic wave in a homogeneous plasma is considered, with particular emphasis on the magnetized case, where ordinary and extraordinary electromagnetic waves travelling normal to B are treated. Two important features are described. First, the penetration of the wave front is shown to be accompanied by ‘radiation’ of low-frequency waves, of which ion cyclotron and lower-hybrid waves are considered here. Next, the presence of a nonlinear, second-harmonic precursor is predicted, containing two natural modes of oscillation, one with exactly twice the frequency of the fundamental, and the other a slightly frequency-shifted contribution. The analysis is readily generalized to waves other than those considered here.

scholarly journals Excitation of extremely low-frequency chorus emissions: The role of background plasma density

2019 ◽  
Vol 3 (1) ◽  
pp. 1-7 ◽  
Author(s):  
XiongDong Yu ◽  
◽  
ZhiGang Yuan ◽  
ShiYong Huang ◽  
Fei Yao ◽  
...  
Keyword(s):  
Plasma Density ◽  
Low Frequency ◽  
Background Plasma ◽  
Extremely Low Frequency

scholarly journals Electromagnetic waves and bursty electron acceleration: implications from Freja

2002 ◽  
Vol 20 (2) ◽  
pp. 139-150 ◽  
Author(s):  
L. Andersson ◽  
J.-E. Wahlund ◽  
J. Clemmons ◽  
B. Gustavsson ◽  
L. Eliasson
Keyword(s):  
Electromagnetic Waves ◽  
Large Scale ◽  
Cutoff Frequency ◽  
Low Frequency ◽  
Correlation Study ◽  
Auroral Oval ◽  
Alfven Wave ◽  
Lower Hybrid ◽  
Field Aligned Current ◽  
Langmuir Probe Measurements

Abstract. Dispersive Alfvén wave activity is identified in four dayside auroral oval events measured by the Freja satellite. The events are characterized by ion injection, bursty electron precipitation below about 1 keV, transverse ion heating and broadband extremely low frequency (ELF) emissions below the lower hybrid cutoff frequency (a few kHz). Large-scale density depletions/cavities, as determined by the Langmuir probe measurements, and strong electrostatic emissions are often observed simultaneously. A correlation study has been carried out between the E and B field fluctuations below 64 Hz and 10 Hz, respectively, (the DC instruments upper threshold) and the characteristics of the precipitating electrons. This study revealed that the energisation of electrons is indeed related to the broadband ELF emissions and that the electrostatic component plays a predominant role during very active magnetospheric conditions. Furthermore, the effect of the ELF electromagnetic emissions on the larger scale field-aligned current systems has been investigated, and it is found that such an effect cannot be detected. Instead, the Alfvénic activity creates a local region of field-aligned currents. It is suggested that dispersive Alfvén waves set up these local field-aligned current regions and, in turn, trigger more electrostatic emissions during certain conditions. In these regions, ions are transversely heated, and large-scale density depletions/cavities may be created during especially active periods.Key words. Ionosphere (particle acceleraton; wave-particle interactions) Magnetospheric physics (auroral phenomena)

Parametric decay of a whistler wave at the difference frequency of two electromagnetic waves in a plasma

1991 ◽  
Vol 45 (1) ◽  
pp. 115-123 ◽  
Author(s):  
S. Guha ◽  
Ruby Sarkar
Keyword(s):  
Electromagnetic Waves ◽  
Low Frequency ◽  
Whistler Wave ◽  
Difference Frequency ◽  
Lower Hybrid ◽  
Ion Heating ◽  
Lower Hybrid Wave ◽  
Electromagnetic Pump ◽  
The Difference ◽  
Pump Waves

A large-amplitude whistler wave excited at the difference frequency of two high-frequency electromagnetic pump waves is shown to decay parametrically into a lower-hybrid wave (LHW) and a low-frequency ion–Bernstein wave (IBW) in a collisionless magnetized multi-ion-species plasma,. A nonlinear dispersion relation describing this parametric interaction process is derived. The low-frequency ponderomotive force along the direction of the external magnetic field leads to the dominant coupling. Possible applications to ion heating in the ionosphere, in the earth's magnetosphere and in laboratory plasmas are discussed.

scholarly journals Studies of Spectral Broadening of the Lower Hybrid Wave Line in the Current-Drive Regimes and Ion Heating at the FT-2 Tokamak

2021 ◽  
Vol 47 (4) ◽  
pp. 329-336
Author(s):  
V. V. Dyachenko ◽  
A. B. Altukhov ◽  
E. Z. Gusakov ◽  
L. A. Esipov ◽  
A. N. Konovalov ◽  
...  
Keyword(s):  
Electromagnetic Waves ◽  
Low Frequency ◽  
Current Drive ◽  
Lower Hybrid ◽  
Ion Heating ◽  
Lower Hybrid Wave ◽  
Acoustic Instability ◽  
Ion Acoustic ◽  
Lower Hybrid Current Drive ◽  
High Frequency Waves

Abstract The experiments at the FT-2 tokamak are described that were focused on clearing up the role of the parametric decay instabilities in decreasing the generation efficiency of the non-inductive current excited by the electromagnetic waves in the lower hybrid frequency range. The most discussed instability of such kind is the decay of the pump wave into the daughter high-frequency waves and the low-frequency ion–acoustic quasi-modes. The studies performed have shown that, under conditions of the FT-2 experiment, the ion–acoustic instability has no decisive effect on the decrease in the efficiency of the lower hybrid current drive.

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