scholarly journals Relativistic and ponderomotive self-focusing of a laser pulse in magnetized plasma

2012 ◽  
Vol 30 (4) ◽  
pp. 659-664 ◽  
Author(s):  
Anamika Sharma ◽  
V.K. Tripathi
Keyword(s):  
Laser Pulse ◽  
Cyclotron Frequency ◽  
Ponderomotive Force ◽  
Beam Width ◽  
Laser Frequency ◽  
Electron Cyclotron ◽  
The Self ◽  
Magnetized Plasma ◽  
Electron Cyclotron Frequency ◽  
Self Focusing

AbstractThe self-focusing of an intense right circularly polarized Gaussian laser pulse in magnetized plasma is studied. The ions are taken to be immobile and relativistic mass effect is incorporated in both the plasma frequency (ωp) and the electron cyclotron frequency (ωc) while determining the ponderomotive force on electrons. The ponderomotive force causes electron expulsion when the effective electron cyclotron frequency is below twice the laser frequency. The nonlinear plasma dielectric function due to ponderomotive and relativistic effects is derived, which is then employed in beam-width parameter equation to study the self-focusing of the laser beam. From this, we estimate the importance of relativistic self-focusing in comparison with ponderomotive self-focusing at moderate laser intensities. The beam width parameter decreases with magnetic field indicating better self-focusing. When the laser intensity is very high, the relativistic gamma factor can be modeled as ${\rm \gamma} = 0.8\left({{{{\rm \omega} _c } / {\rm \omega} }} \right)+ \sqrt {1 + a_0^2 }$γ=0.8(ωc/ω)+1+a02 where ω and a0 are the laser frequency and the normalized laser field strength, respectively. The cyclotron effects on the self-focusing of laser pulse are reduced at high field strengths.

Axially symmetric self-focusing of whistler waves

1984 ◽  
Vol 31 (2) ◽  
pp. 209-223 ◽  
Author(s):  
V. I. Karpman ◽  
R. N. Kaufman ◽  
A. G. Shagalov
Keyword(s):  
Cyclotron Frequency ◽  
Electron Cyclotron ◽  
The Self ◽  
Schrodinger Equations ◽  
Schrödinger Equations ◽  
Axially Symmetric ◽  
Whistler Waves ◽  
Electron Cyclotron Frequency ◽  
Self Focusing ◽  
Homogeneous Wave

The self-focusing of whistler waves in a low-β plasma is considered. Axially symmetric solutions of the MHD and Schrödinger equations are found that describe stationary and homogeneous wave beams together with the plasma ducts in which they are trapped.The self-focusing occurs both at ω < ½ωc and ω > ½ωc where ωc is the electron cyclotron frequency. The wave leakage which takes place in some types of duct and pre vents self-focusing from developing is investigated in detail.

scholarly journals Effect of plasma channel non-uniformity on resonant third harmonic generation

2013 ◽  
Vol 31 (3) ◽  
pp. 531-537 ◽  
Author(s):  
Anuraj Panwar ◽  
Chang-Mo Ryu ◽  
Ashok Kumar
Keyword(s):  
Laser Pulse ◽  
Harmonic Generation ◽  
Plasma Channel ◽  
Second Harmonic ◽  
Third Harmonic Generation ◽  
Laser Frequency ◽  
The Self ◽  
Third Harmonic ◽  
The Third ◽  
Self Focusing

AbstractWe study the generation of resonant third harmonic laser radiation in a density non-uniform rippled plasma channel. An introduction of plasma channel non-uniformity strongly enhances the self-focusing and compression of main laser pulse at lower powers. In a deeper plasma channel, self-focusing is less sensitive to laser amplitude variation but increases compression. Plasma density ripple ‘nq’ leading to resonant third harmonic generation when kq = 4ω2p/3meω0cγ0, where ‘ω’p is electron plasma frequency, ‘ω0’ is laser frequency, and ‘γ0’ is the electron Lorentz factor. Third harmonic is produced through the beating of ponderomotive force induced second harmonic density oscillations and the oscillatory velocity of electrons at main laser frequency. The self-focusing and compression of the fundamental pulse periodically enhances the intensity of the third-harmonic pulse at lower powers of main laser. In a deeper plasma channel, the third harmonic power is less effective by self-focusing and the compression of main laser, and increase with main laser pulse power.

scholarly journals Self-focusing of asymmetric cosh-Gaussian laser beams propagating through collisionless magnetized plasma

2017 ◽  
Vol 35 (4) ◽  
pp. 670-676 ◽  
Author(s):  
B. D. Vhanmore ◽  
S. D. Patil ◽  
A. T. Valkunde ◽  
T. U. Urunkar ◽  
K. M. Gavade ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Ponderomotive Force ◽  
Beam Width ◽  
Magnetized Plasma ◽  
Laser Beams ◽  
Gaussian Beams ◽  
Equation Approach ◽  
Kutta Method ◽  
Runge Kutta Method ◽  
Self Focusing

AbstractIn this paper, self-focusing of asymmetric cosh-Gaussian laser beams in collisionless magnetized plasma has been studied. The non-linearity in dielectric constant considered herein is mainly due to the ponderomotive force. The non-linear coupled differential equations for the beam width parameters in transverse dimensions of the beam have been obtained by using WKB and paraxial approximations under parabolic equation approach. The numerical computation is completed by using fourth-order Runge–Kutta method. The effect of unlike decentered parameters in both transverse dimensions of the beam on self-focusing of cosh-Gaussian beams has been presented. Further, the effect of the static magnetic field and polarization modes of the laser has been explored.

scholarly journals Electron acceleration by ponderomotive force in magnetized quantum plasma

2017 ◽  
Vol 35 (2) ◽  
pp. 252-258 ◽  
Author(s):  
A.K. Singh ◽  
S. Chandra
Keyword(s):  
Laser Pulse ◽  
Cyclotron Frequency ◽  
Ponderomotive Force ◽  
Electron Acceleration ◽  
Basic Mechanism ◽  
Laser Frequency ◽  
Quantum Plasma ◽  
Circularly Polarized ◽  
Ponderomotive Potential ◽  
Density Plasma

AbstractThe possibilities of electron acceleration by ponderomotive force of a circularly polarized laser pulse in magnetized quantum plasma have been explored. The basic mechanism involves acceleration of electron by the axial gradient in the ponderomotive potential of the laser. The quantum effects have been taken into account for a high-density plasma. The ponderomotive force of the laser is resonantly enhanced when Doppler up-shifted laser frequency equals the cyclotron frequency.

Combined influence of axial electron temperature and exponential plasma density ramp on the self-focusing of a chirped laser in plasma

2020 ◽  
Vol 75 (7) ◽  
pp. 671-675
Author(s):  
Niti Kant ◽  
Vishal Thakur
Keyword(s):  
Electron Temperature ◽  
Pulse Laser ◽  
Plasma Density ◽  
Beam Width ◽  
Spot Size ◽  
Higher Order ◽  
The Self ◽  
Chirped Pulse ◽  
Self Focusing ◽  
Paraxial Ray

AbstractAn analysis of the self-focusing of highly intense chirped pulse laser under exponential plasma density ramp with higher order value of axial electron temperature has been done. Beam width parameter is derived by using paraxial ray approximation and then solved numerically. It is seen that self-focusing of chirped pulse laser is intensely affected by the higher order values of axial electron temperature. Further, influence of exponential plasma density ramp is studied and it is concluded that self-focusing of laser enhances and occurs earlier. On the other hand defocusing of beam reduces to the great extent. It is noticed that the laser spot size reduces significantly under joint influence of the density ramp and the axial electron temperature. Present analysis may be useful for the analysis of quantum dots, the laser induced fusion and etc.

scholarly journals Radial variation of whistler-mode chorus: first results from the STAFF/DWP instrument on board the Double Star TC-1 spacecraft

2005 ◽  
Vol 23 (8) ◽  
pp. 2937-2942 ◽  
Author(s):  
O. Santolík ◽  
E. Macúšová ◽  
K. H. Yearby ◽  
N. Cornilleau-Wehrlin ◽  
H. StC. K. Alleyne
Keyword(s):  
Cyclotron Frequency ◽  
Power Spectra ◽  
Double Star ◽  
Electron Cyclotron ◽  
Radial Variation ◽  
Whistler Mode ◽  
Electron Cyclotron Frequency ◽  
The Earth ◽  
First Results ◽  
Initial Results

Abstract. We use the first measurements of the STAFF/DWP instrument on the Double Star TC-1 spacecraft to investigate whistler-mode chorus. We present initial results of a systematic study on radial variation of dawn chorus. The chorus events show an increased intensity at L parameter above 6. This is important for the possible explanation of intensifications of chorus, which were previously observed closer to the Earth at higher latitudes. Our results also indicate that the upper band of chorus at frequencies above one-half of the electron cyclotron frequency disappears for L above 8. The lower band of chorus is observed at frequencies below 0.4 of the electron cyclotron frequency up to L of 11-12. The maxima of the chorus power spectra are found at slightly lower frequencies compared to previous studies. We do not observe any distinct evolution of the position of the chorus frequency band as a function of L. More data of the TC-1 spacecraft are needed to verify these initial results and to increase the MLT coverage.

Generation of Efficient Terahertz Radiation by Relativistic Self-Focusing of A Cosh-Gaussian Laser Beam in A Magnetized Plasma

2021 ◽  
Author(s):  
Gunjan Purohit ◽  
Bineet Gaur ◽  
Pradeep Kothiyal ◽  
Amita Raizada
Keyword(s):  
Laser Beam ◽  
Numerical Study ◽  
The Self ◽  
Magnetized Plasma ◽  
Thz Radiation ◽  
Gaussian Laser Beam ◽  
Plasma Parameters ◽  
Gaussian Profile ◽  
Self Focusing ◽  
Incident Laser Intensity

Abstract This paper presents a scheme for the generation of terahertz (THz) radiation by self-focusing of a cosh-Gaussian laser beam in the magnetized and rippled density plasma, when relativistic nonlinearity is operative. The strong coupling between self-focused laser beam and pre-existing density ripple produces nonlinear current that originates THz radiation. THz radiation is produced by the interaction of the cosh-Gaussian laser beam with electron plasma wave under the appropriate phase matching conditions. Expressions for the beamwidth parameter of cosh-Gaussian laser beam and the electric vector of the THz radiation have been obtained using higher-order paraxial theory and solved numerically. The self-focusing of the cosh-Gaussian laser beam and its effect on the generated THz amplitude have been studied for specific laser and plasma parameters. Numerical study has been performed on various values of the decentered parameter, incident laser intensity, magnetic field, and relative density. The results have also been compared with the paraxial region as well as the Gaussian profile of laser beam. Numerical results suggest that the self-focusing of the cosh-Gaussian laser beam and the amplitude of THz radiation increase in the extended paraxial region compared to the paraxial region. It is also observed that the focusing of the cosh-Gaussian laser beam in the magnetized plasma and the amplitude of the THz radiation increases at higher values of the decentered parameter.

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