scholarly journals Low frequency waves in plasmas with spatially varying electron temperature

2000 ◽  
Vol 18 (12) ◽  
pp. 1613-1622 ◽  
Author(s):  
P. Guio ◽  
S. Børve ◽  
H. L. Pécseli ◽  
J. Trulsen
Keyword(s):  
Numerical Simulation ◽  
Electron Temperature ◽  
Acoustic Waves ◽  
Low Frequency ◽  
Plasma Temperature ◽  
Electrostatic Waves ◽  
Radio Science ◽  
Particle In Cell ◽  
Ionosphere Plasma ◽  
Low Frequency Waves

Abstract. Low frequency electrostatic waves are studied in magnetized plasmas with an electron temperature which varies with position in a direction perpendicular to the magnetic field. For wave frequencies below the ion cyclotron frequency, the waves need not follow any definite dispersion relation. Instead a band of phase velocities is allowed, with a range of variation depending on the maximum and minimum values of the electron temperature. Simple model equations are obtained for the general case which can be solved to give the spatial variation of a harmonically time varying potential. A simple analytical model for the phenomenon is presented and the results are supported by numerical simulations carried out in a 2½-dimensional particle-in-cell numerical simulation. We find that when the electron temperature is striated along B0 and low frequency waves (ω ≪ Ωci) are excited in this environment, then the intensity of these low frequency waves will be striated in a manner following the electron temperature striations. High frequency ion acoustic waves (ω ≫ Ωci) will on the other hand have a spatially more uniform intensity distribution.Key words: Ionosphere (plasma temperature and density) · Radio science (waves in plasma) · Space plasma physics (numerical simulation studies)

scholarly journals Proparyation of Low frequency microwave in dusty Plasma

2008 ◽  
Vol 5 (3) ◽  
pp. 374-378
Author(s):  
Baghdad Science Journal
Keyword(s):  
Dusty Plasma ◽  
Acoustic Waves ◽  
Coupling Parameter ◽  
Low Frequency ◽  
Dust Particles ◽  
Ion Acoustic Waves ◽  
Electrostatic Waves ◽  
Wave Dynamics ◽  
Special Cases ◽  
Low Frequency Waves

The numerical simulation for the low frequency waves in dusty plasma has been studied. The studying was done by taking two special cases depending on the direction of the propagation of the wave:First, when the propagation is parallel to the magnetic field K//B,this mode is called acoustic mode.Second,when K B this mode is called cyclotron mode.In addition, every one of the two modes divided into two modes depending on the range of the frequency.The Coulomb coupling parameter was studied, with temperature T,density of the dust particles Nd ,and the charge of the particle Qd.The low frequency electrostatic waves in dusty grains were studied. Also, the properties of ion-acoustic waves and ion-cyclotron waves are shown to modify even through the dust grains do not participate in the wave dynamics. If the dust dynamics induced in the analysis, new “ dust modes “ appear.

Coupled Langmuir and nonlinear ion acoustic waves in the presence of non-thermal electrons

2009 ◽  
Vol 75 (2) ◽  
pp. 193-202 ◽  
Author(s):  
H. ALINEJAD ◽  
P. A. ROBINSON ◽  
O. SKJAERAASEN ◽  
I. H. CAIRNS
Keyword(s):  
Mach Number ◽  
Acoustic Waves ◽  
High Frequency ◽  
Strong Field ◽  
Low Frequency ◽  
Thermal Electron ◽  
Electrostatic Waves ◽  
Envelope Solitons ◽  
Langmuir Soliton ◽  
Langmuir Solitons

AbstractA new set of equations describing the coupling of high-frequency electrostatic waves with ion fluctuations is obtained taking into account a non-thermal electron distribution. It is shown that there exist stationary envelope solitons which have qualitatively different structures from the solutions reported earlier. In particular, the Langmuir field envelopes are found with similar width and strong field intensities in comparison to the isothermal case. It is also shown that the presence of the fast or non-thermal electrons significantly modifies the nature of Langmuir solitons in the transition from a single-hump solution to a double-hump solution as the Mach number increases to unity. The low-frequency electrostatic potential associated with the high-frequency Langmuir field has the usual single-dip symmetric structure whose amplitude increases with increasing Mach number. Furthermore, the dip at the center of the double-hump Langmuir soliton is found to become smaller as the proportion of non-thermal electrons increases.

Scattering of Plane Waves by a Constriction

2011 ◽  
Author(s):  
E. Alenius ◽  
M. A˚bom ◽  
L. Fuchs
Keyword(s):  
Acoustic Waves ◽  
Plane Waves ◽  
Low Frequency ◽  
Acoustic Energy ◽  
Flow Noise ◽  
Times Series ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Low Frequency Waves ◽  
Good Agreement

Liner scattering of low frequency waves by an orifice plate has been studied using Large Eddy Simulation and an acoustic two-port model. The results have been compared to measurements with good agreement for waves coming from the downstream side. For waves coming from the upstream side the reflection is over-predicted, indicating that not enough of the acoustic energy is converted to vorticity at the upstream edge of the plate. Furthermore, the sensitivity to the amplitude of the acoustic waves has been studied, showing difficulties to simultaneously keep the amplitude low enough for linearity and high enough to suppress flow noise with the relatively short times series available in LES.

Solitary Langmuir waves in two-electron temperature plasma

2013 ◽  
Vol 80 (3) ◽  
pp. 405-415
Author(s):  
V. V. Prudkikh
Keyword(s):  
Electron Temperature ◽  
Acoustic Waves ◽  
Low Frequency ◽  
Langmuir Wave ◽  
Wave Interaction ◽  
Plasma Parameters ◽  
Temperature Plasma ◽  
Langmuir Waves ◽  
Peak Structure ◽  
Langmuir Soliton

Nonlinear interaction of Langmuir and ion-acoustic waves in two-electron temperature plasma is investigated. New integrable wave interaction regime was discovered, this regime corresponds to the Langmuir soliton with three-hump amplitude, propagating with a speed close to the ion–sound speed in the conditions of strong non-isothermality of electronic components. It was discovered that besides the known analytical solution in the form of one- and two-hump waves, there exists a range of solutions in the form of solitary waves, which in the form of envelope has multi-peak structure and differs from the standard profiles described by hyperbolic functions. In case of fixed plasma parameters, different group velocities correspond to the waves with different number of peaks. It is found that the Langmuir wave package contains both even and uneven numbers of oscillations. Low-frequency potential here has uneven number of peaks. Interrelation of obtained and known earlier results are also discussed.

The parametric excitation of kinetic Alfvén waves by a magnetic pump

1981 ◽  
Vol 26 (2) ◽  
pp. 253-266 ◽  
Author(s):  
N. F. Cramer ◽  
I. J. Donnelly
Keyword(s):  
Finite Temperature ◽  
Acoustic Waves ◽  
Temperature Effects ◽  
Mode Conversion ◽  
Low Frequency ◽  
Alfven Waves ◽  
Alfven Wave ◽  
Alfvén Waves ◽  
Ion Acoustic Wave ◽  
Low Frequency Waves

The parametric decay of a magneto-acoustic pump wave into low-frequency waves modified by finite temperature effects is considered. The excited waves are the kinetic Alfvén wave and the ion-acoustic wave. The former wave plays an important role in linear heating schemes employing the mode conversion of magneto-acoustic waves at the Alfvén resonance. Here we calculate the parametric growth rates and pump thresholds for excitation of these waves. The main result is that finite temperature effects tend to reduce the growth rate of Alfvén waves.

scholarly journals On the mechanism of the post-midnight winter <i>N<sub>m</sub>F<sub>2</sub></i> enhancements: dependence on solar activity

2000 ◽  
Vol 18 (11) ◽  
pp. 1422-1434 ◽  
Author(s):  
A. V. Mikhailov ◽  
M. Förster ◽  
T. Y. Leschinskaya
Keyword(s):  
Solar Activity ◽  
Electron Temperature ◽  
Electron Density ◽  
Opposite Sign ◽  
Plasma Temperature ◽  
Ionosphere Plasma ◽  
Recombination Efficiency ◽  
Thermospheric Winds ◽  
Flux Increase ◽  
Different Levels

Abstract. The mechanism of the NmF2 peak formation at different levels of solar activity is analyzed using Millstone Hill IS radar observations. The hmF2 nighttime increase due to thermospheric winds and the downward plasmaspheric fluxes are the key processes responsible for the NmF2 peak formation. The electron temperature follows with the opposite sign the electron density variations in this process. This mechanism provides a consistency with the Millstone Hill observations on the set of main parameters. The observed decrease of the nighttime NmF2 peak amplitude with solar activity is due to faster increasing of the recombination efficiency compared to the plasmaspheric flux increase. The E×B plasma drifts are shown to be inefficient for the NmF2 nighttime peak formation at high solar activity.Key words: Ionosphere (ionosphere-atmosphere interactions; mid-latitude ionosphere; plasma temperature and density)

Instability of low-frequency waves in a cold plasma mixed with hot electrons

1985 ◽  
Vol 33 (3) ◽  
pp. 437-441 ◽  
Author(s):  
Hiromitsu Hamabata ◽  
Tomikazu Namikawa
Keyword(s):  
Equilibrium State ◽  
Electron Temperature ◽  
Cold Plasma ◽  
Low Frequency ◽  
Hot Electrons ◽  
Hot Electron ◽  
Temperature Anisotropy ◽  
First Order ◽  
Cold Electrons ◽  
Low Frequency Waves

The instability of low-frequency waves in a cold plasma mixed with hot electrons is investigated using the first-order CGL equations for electrons. It is assumed that in an equilibrium state the electrons consist of two components, cold electrons and hot electrons with bi-Maxwellians. It is shown that low-frequency waves with right-hand polarization can be generated by the hot electron temperature anisotropy and the existence of cold electrons.

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