Linear conversion in a magnetized plasma with density gradient parallel to the magnetic field

1983 ◽  
Vol 30 (2) ◽  
pp. 179-192 ◽  
Author(s):  
E. Mjølhus
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Wave ◽  
Density Gradient ◽  
Conversion Coefficient ◽  
Magnetized Plasma ◽  
Angle Of Incidence ◽  
Linear Conversion ◽  
The Magnetic Field

The problem of linear conversion of an ordinary polarized electromagnetic wave in a magnetized plasma with density gradient parallel to the magnetic field is considered. An expression for the conversion coefficient as a function of angle of incidence, WKB parameter and magnetic field is obtained. The magnetic field leads to a narrowing of the range of angles of incidence leading to linear conversion, compared with the unmagnetized case.

Theory of Raman sidescatter from a magnetized plasma

1984 ◽  
Vol 32 (2) ◽  
pp. 331-346 ◽  
Author(s):  
H. C. Barr ◽  
T. J. M. Boyd ◽  
R. Rankin
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Wave ◽  
Growth Rates ◽  
Scattered Light ◽  
Critical Density ◽  
Magnetized Plasma ◽  
Frequency Shifts ◽  
Wave Growth ◽  
Circularly Polarized ◽  
The Magnetic Field

The effects of a d.c. magnetic field on stimulated Raman sidescatter from laser-produced plasmas is studied. For exact sidescatter along the magnetic field, the Raman instability separates into two distinct decays in which the scattered light is either a right (RHCP) or left (LHCP) circularly polarized electromagnetic wave. Growth rates of the instabilities can be enhanced in the former case but are diminished in the latter. The magnetic field induced effects are greatest near the quarter critical density where frequency shifts can be especially significant, being equal to ± ¼Ωc for decay into RHCP and LHCP waves, respectively.

scholarly journals Second-harmonic generation by an obliquely incident s-polarized laser from a magnetized plasma

2016 ◽  
Vol 34 (2) ◽  
pp. 276-283 ◽  
Author(s):  
Deep Kumar Kuri ◽  
Nilakshi Das
Keyword(s):  
Magnetic Field ◽  
Second Harmonic Generation ◽  
Harmonic Generation ◽  
Conversion Efficiency ◽  
Second Harmonic ◽  
Magnetized Plasma ◽  
Angle Of Incidence ◽  
Obliquely Incident ◽  
Relativistic Factor ◽  
The Magnetic Field

AbstractSecond-harmonic generation by an obliquely incident s-polarized laser from an underdense plasma in the presence of a magnetic field has been investigated analytically. An expression for the relativistic factor γ has been obtained in the presence of magnetic field. The efficiency of second-harmonic radiation η has been obtained as a function of angle of incidence θ, normalized electric field amplitude of laser beam a0, normalized electron density ${\rm \omega} _{\rm p}^2 /{{\rm \omega} ^2}$, and magnetic field b. It is observed that γ increases with b. In turn, the conversion efficiency decreases with an increase in b. It is seen that the conversion efficiency is affected by the magnetic field due to the modified relativistic factor. In the absence of magnetic field, η increases with a0 and θ. However, in the presence of magnetic field, the conversion efficiency starts decreasing as the magnetic field is increased.

Electrostatic modes in a magnetized plasma with a longitudinal density gradient

1983 ◽  
Vol 29 (2) ◽  
pp. 177-194 ◽  
Author(s):  
J. E. Maggs ◽  
G. J. Morales
Keyword(s):  
Magnetic Field ◽  
Density Gradient ◽  
Low Frequency ◽  
Resonant Absorption ◽  
Plasma Resonance ◽  
Magnetized Plasma ◽  
Auroral Ionosphere ◽  
Long Wavelength ◽  
Plasma Theory ◽  
The Magnetic Field

An analytic study is made of the electrostatic mode structures which exist between the upper-hybrid cut-off and the plasma resonance in a plasma in which the zero-order density gradient points along the magnetic field. In general the solutions consist of long-wavelength cold modes which are converted to short-wavelength Bohm-Gross modes near plasma resonance. However, there exist certain discrete angles of propagation at which finite solutions exist that can be described solely in terms of cold plasma theory. The relevance of these processes to resonant absorption experiments in the auroral ionosphere is considered. A brief study is made of the changes produced by a finite angle between the density gradient and the magnetic field. The possibility of finding analogous low-frequency structures is also investigated.

scholarly journals Lepton-driven Nonresonant Streaming Instability

2021 ◽  
Vol 923 (2) ◽  
pp. 208
Author(s):  
Siddhartha Gupta ◽  
Damiano Caprioli ◽  
Colby C. Haggerty
Keyword(s):  
Magnetic Field ◽  
Laboratory Experiments ◽  
Magnetized Plasma ◽  
Ion Current ◽  
Pulsar Wind Nebulae ◽  
Particle In Cell ◽  
Streaming Instability ◽  
Electrons And Positrons ◽  
Pulsar Wind ◽  
The Magnetic Field

Abstract A strong super-Alfvénic drift of energetic particles (or cosmic rays) in a magnetized plasma can amplify the magnetic field significantly through nonresonant streaming instability (NRSI). While the traditional analysis is done for an ion current, here we use kinetic particle-in-cell simulations to study how the NRSI behaves when it is driven by electrons or by a mixture of electrons and positrons. In particular, we characterize the growth rate, spectrum, and helicity of the unstable modes, as well the level of the magnetic field at saturation. Our results are potentially relevant for several space/astrophysical environments (e.g., electron strahl in the solar wind, at oblique nonrelativistic shocks, around pulsar wind nebulae), and also in laboratory experiments.

The Unique Property in Magnetic Noise of Spin Modulated Atomic Magnetometer

2018 ◽  
Vol 787 ◽  
pp. 75-80
Author(s):  
Xiao Fei Wang ◽  
Ji Min Li
Keyword(s):  
Magnetic Field ◽  
Conversion Coefficient ◽  
Transverse Relaxation Time ◽  
Unique Property ◽  
Magnetic Noise ◽  
Transverse Relaxation ◽  
Polarization Signal ◽  
Measurement Experiment ◽  
The Magnetic Field ◽  
Higher Sensitivity

This paper presents a spin modulated atomic magnetometer, different from other kinds of atomic magnetometers, the conversion coefficient between the polarization signal and the magnetic field to be measured is independent of the transverse relaxation time, which means that the higher sensitivity can be achieved when polarization is kept constant. For better understanding, the magnetic noise of spin modulated magnetometer is demonstrated and compared to SERF magnetometer. The magnetic noise measurement experiment is designed, the experimental results are consistent with the theoretical prediction. This paper validate the unique property of spin modulated magnetometer and this property will play an important role in guiding the optimization of future experiments.

scholarly journals Dependence on ion temperature of shallow-angle magnetic presheaths with adiabatic electrons

2019 ◽  
Vol 85 (6) ◽  
Author(s):  
Alessandro Geraldini ◽  
F. I. Parra ◽  
F. Militello
Keyword(s):  
Magnetic Field ◽  
Fluid Model ◽  
Boltzmann Distribution ◽  
Distribution Functions ◽  
Magnetized Plasma ◽  
Electron Mass ◽  
Ion Temperature ◽  
Ion Distribution ◽  
Ionic Charge ◽  
The Magnetic Field

The magnetic presheath is a boundary layer occurring when magnetized plasma is in contact with a wall and the angle $\unicode[STIX]{x1D6FC}$ between the wall and the magnetic field $\boldsymbol{B}$ is oblique. Here, we consider the fusion-relevant case of a shallow-angle, $\unicode[STIX]{x1D6FC}\ll 1$ , electron-repelling sheath, with the electron density given by a Boltzmann distribution, valid for $\unicode[STIX]{x1D6FC}/\sqrt{\unicode[STIX]{x1D70F}+1}\gg \sqrt{m_{\text{e}}/m_{\text{i}}}$ , where $m_{\text{e}}$ is the electron mass, $m_{\text{i}}$ is the ion mass, $\unicode[STIX]{x1D70F}=T_{\text{i}}/ZT_{\text{e}}$ , $T_{\text{e}}$ is the electron temperature, $T_{\text{i}}$ is the ion temperature and $Z$ is the ionic charge state. The thickness of the magnetic presheath is of the order of a few ion sound Larmor radii $\unicode[STIX]{x1D70C}_{\text{s}}=\sqrt{m_{\text{i}}(ZT_{\text{e}}+T_{\text{i}})}/ZeB$ , where e is the proton charge and $B=|\boldsymbol{B}|$ is the magnitude of the magnetic field. We study the dependence on $\unicode[STIX]{x1D70F}$ of the electrostatic potential and ion distribution function in the magnetic presheath by using a set of prescribed ion distribution functions at the magnetic presheath entrance, parameterized by $\unicode[STIX]{x1D70F}$ . The kinetic model is shown to be asymptotically equivalent to Chodura’s fluid model at small ion temperature, $\unicode[STIX]{x1D70F}\ll 1$ , for $|\text{ln}\,\unicode[STIX]{x1D6FC}|>3|\text{ln}\,\unicode[STIX]{x1D70F}|\gg 1$ . In this limit, despite the fact that fluid equations give a reasonable approximation to the potential, ion gyro-orbits acquire a spatial extent that occupies a large portion of the magnetic presheath. At large ion temperature, $\unicode[STIX]{x1D70F}\gg 1$ , relevant because $T_{\text{i}}$ is measured to be a few times larger than $T_{\text{e}}$ near divertor targets of fusion devices, ions reach the Debye sheath entrance (and subsequently the wall) at a shallow angle whose size is given by $\sqrt{\unicode[STIX]{x1D6FC}}$ or $1/\sqrt{\unicode[STIX]{x1D70F}}$ , depending on which is largest.

Fast magnetic field penetration into low resistivity plasma

2017 ◽  
Vol 83 (1) ◽  
Author(s):  
Amnon Fruchtman
Keyword(s):  
Magnetic Field ◽  
Energy Dissipation ◽  
Electric Field ◽  
Density Gradient ◽  
Magnetic Energy ◽  
Measured Velocity ◽  
Magnetic Field Penetration ◽  
The Magnetic Field ◽  
Uniform Plasma ◽  
Field Penetration

Penetration of a magnetic field into plasma that is faster than resistive diffusion can be induced by the Hall electric field in a non-uniform plasma. This mechanism explained successfully the measured velocity of the magnetic field penetration into pulsed plasmas. Major related issues have not yet been resolved. Such is the theoretically predicted, but so far not verified experimentally, high magnetic energy dissipation, as well as the correlation between the directions of the density gradient and of the field penetration.

Electromagnetic wave backscattering across a magnetic field in a bounded plasma

1979 ◽  
Vol 22 (1) ◽  
pp. 85-96
Author(s):  
Joseph E. Willett ◽  
Sinan Bilikmen ◽  
Behrooz Maraghechi
Keyword(s):  
Magnetic Field ◽  
Numerical Study ◽  
Magnetized Plasma ◽  
Absolute Instability ◽  
Moment Equations ◽  
Homogeneous Plasma ◽  
Coupled Equations ◽  
Bounded Plasma ◽  
The Moment ◽  
The Magnetic Field

The stimulated backscattering of electromagnetic ordinary waves from extraordinary waves propagating normal to a magnetic field in a plasma of finite length is studied. A pair of coupled differential equations for the amplitudes of the backscattered and scatterer waves is derived from Maxwell's equations and the moment equations for an inhomogeneous magnetized plasma. Solution of the coupled equations for a homogeneous plasma yields an expression for the growth rate of the absolute instability as a function of plasma length and damping rates of the product waves. The convective regime in which only spatial amplification occurs is discussed. A numerical study of the effects of the magnetic field on Raman and Brillouin backscattering is presented.

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