Scattering of Electromagnetic Waves in the Presence of Wave Turbulence Excited by a Flow with Velocity Shear

2010 ◽  
Author(s):  
Vladimir Sotnikov ◽  
Jean-Noel Leboeuf ◽  
Saba Mudaliar
Keyword(s):  
Electromagnetic Waves ◽  
Velocity Shear ◽  
Wave Turbulence

Velocity-shear instability of relativistic electron beams: a systematic exploration of the entire(ω, k) space

1992 ◽  
Vol 48 (3) ◽  
pp. 453-464
Author(s):  
D. Heristchi ◽  
S. Cuperman
Keyword(s):  
Relativistic Electron ◽  
Electromagnetic Waves ◽  
Electron Beams ◽  
Velocity Shear ◽  
Shear Instability ◽  
Marginal Stability ◽  
Physical Parameters ◽  
Complex Frequency ◽  
Relativistic Electron Beams ◽  
Solution Methods

Using the exact solution methods developed and illustrated previously, we systematically explore (ω, k) space in order to determine all the unstable modes of velocity-shear-produced electromagnetic waves in magnetized, relativistic electron beams (here ω and k are the complex frequency and real wavenumber). This is done for various physical parameters of the problem, namely shear factor and ratio of pipe to beam radii. The solution of the dispersion relation is supplemented by a marginal stability analysis based on the behaviour of the turning points of the purely real-frequency solution ωr, (k): these are bifurcation points where complex solutions originate or terminate.

Efficiency of electromagnetic emission by electrostatic turbulence in solar plasmas with density inhomogeneities

2020 ◽  
Author(s):  
Catherine Krafft ◽  
Alexander Volokitin
Keyword(s):  
Electromagnetic Waves ◽  
Langmuir Wave ◽  
Density Fluctuations ◽  
Radiation Efficiency ◽  
Wave Turbulence ◽  
Radiation Mechanism ◽  
Constant Frequency ◽  
Electrostatic Wave ◽  
Electromagnetic Emissions ◽  
Solar Plasmas

<p>A new method to calculate semi-analytically the radiation efficiency of electromagnetic waves emitted at specific frequencies by electrostatic wave turbulence in solar plasmas with random density fluctuations is presented. It is applied to the case of electromagnetic emissions radiated at the fundamental plasma frequency ω<sub>p</sub> by beam-driven Langmuir wave turbulence during Type III solar bursts. It is supposed that the main radiation mechanism is the linear conversion of electrostatic to electromagnetic waves on the background plasma density fluctuations, at constant frequency. Due to the presence of such inhomogeneities, the rates of electromagnetic radiation are modified compared to the case of uniform plasmas. Results show that the radiation efficiency of Langmuir wave turbulence into electromagnetic emissions at ω<sub>p</sub> is nearly constant asymptotically, the electromagnetic energy density growing linearly with time, and is proportional to the average level of density fluctuations. Comparisons with another analytical method developed by the authors and with space observations are satisfactory.</p>

Electromagnetic radiation from upper-hybrid wave turbulence driven by electron beams in solar plasmas

2020 ◽  
Author(s):  
Gaetan Gauthier ◽  
Catherine Krafft ◽  
Philippe Savoini
Keyword(s):  
Electromagnetic Radiation ◽  
Electromagnetic Waves ◽  
Large Scale ◽  
Solar Radio ◽  
Electron Beams ◽  
Energetic Electron ◽  
Wave Turbulence ◽  
Hybrid Wave ◽  
Langmuir Waves ◽  
Type Iii

<p>Solar radio bursts of Type III are believed to result from a sequence of physical processes ultimately leading to electromagnetic wave emissions near the electron plasma frequency ω<sub>p</sub> and its harmonic 2ω<sub>p</sub>. The radiation bursts are due to energetic electron beams accelerated during solar flares. When propagating in the solar corona and the interplanetary wind, these fluxes excite Langmuir and upper-hybrid wave turbulence, which can be further transformed into electromagnetic radiation near the frequencies ω<sub>p</sub> and 2ω<sub>p</sub>.</p><p>It is believed that, in a homogeneous plasma, Langmuir turbulence evolves due to three-wave interaction processes, such as the fusion of Langmuir waves L with sound waves S leading to the formation of electromagnetic waves T<sub>ωp</sub> at ω<sub>p</sub> or the decay of L-waves into S-waves and T<sub>ω</sub><sub>p</sub>-waves. On the other hand, the electromagnetic waves radiated at 2ω<sub>p</sub> should arise from the coalescence L + L’ --> T<sub>2ω</sub><sub>p</sub> of Langmuir waves L generated by the beam with Langmuir waves L’ coming from the electrostatic decay L --> L’ +  S.</p><p>Large-scale 2D3V Particle-In-Cell simulations have been performed with the fully kinetic code Smilei [Derouillat et al., 2018], using parameters typical of Type III solar radio busts. The excitation of upper-hybrid wave turbulence by energetic electron beams propagating in magnetized plasmas leads ultimately to electromagnetic emissions near the fundamental and the harmonic plasma frequencies.</p><p><em>Derouillat et al. , Comput. Phys. Commun., 222, 351, <strong>2017</strong>.</em></p>

Exact solution of the dispersion equation for electromagnetic waves in sheared relativistic electron beams

1992 ◽  
Vol 48 (1) ◽  
pp. 59-70 ◽  
Author(s):  
S. Cuperman ◽  
D. Heristchi
Keyword(s):  
Dispersion Equation ◽  
Electromagnetic Waves ◽  
Bessel Functions ◽  
Electron Beams ◽  
Velocity Shear ◽  
Shear Instability ◽  
Beam Radius ◽  
Slow Mode ◽  
Modified Bessel Functions ◽  
Relativistic Electron Beams

The transcendental dispersion equation for electromagnetic waves propagating in the slow mode in sheared non-neutral relativistic cylindrical electron beams in strong applied magnetic fields is solved exactly. Thus, rather than truncated power series for the modified Bessel functions involved, use is made of modern algorithms able to compute such functions up to 18-digit accuracy. Consequently, new and significantly more important branches of the velocity shear instability are found. When the shear-factor and/or the geometrical parameter a/b (pipe-to-beam radius ratio) are increased, the unstable branches join, and the higher-frequency, larger-wavenumber modes are significantly enhanced. Since analytical solutions of the exact dispersion relation cannot be obtained, it is suggested that in all similar cases the methods proposed and demonstrated here should be used to carry out a rigorous stability analysis.

Seti Space Missions

1997 ◽  
Vol 161 ◽  
pp. 761-776 ◽  
Author(s):  
Claudio Maccone
Keyword(s):  
Electromagnetic Waves ◽  
Space Missions ◽  
Gravitational Lens ◽  
The Sun ◽  
Space Antenna ◽  
Focal Distance ◽  
Large Space ◽  
The Earth ◽  
Space Antennas ◽  
New Space

AbstractSETI from space is currently envisaged in three ways: i) by large space antennas orbiting the Earth that could be used for both VLBI and SETI (VSOP and RadioAstron missions), ii) by a radiotelescope inside the Saha far side Moon crater and an Earth-link antenna on the Mare Smythii near side plain. Such SETIMOON mission would require no astronaut work since a Tether, deployed in Moon orbit until the two antennas landed softly, would also be the cable connecting them. Alternatively, a data relay satellite orbiting the Earth-Moon Lagrangian pointL2would avoid the Earthlink antenna, iii) by a large space antenna put at the foci of the Sun gravitational lens: 1) for electromagnetic waves, the minimal focal distance is 550 Astronomical Units (AU) or 14 times beyond Pluto. One could use the huge radio magnifications of sources aligned to the Sun and spacecraft; 2) for gravitational waves and neutrinos, the focus lies between 22.45 and 29.59 AU (Uranus and Neptune orbits), with a flight time of less than 30 years. Two new space missions, of SETI interest if ET’s use neutrinos for communications, are proposed.

Microwaves: Application in Electron Microscopy

1990 ◽  
Vol 48 (3) ◽  
pp. 140-141
Author(s):  
Anthony S-Y Leong ◽  
David W Gove
Keyword(s):  
Electron Microscopy ◽  
Light Microscopy ◽  
Chemical Reactions ◽  
Electromagnetic Waves ◽  
Tissue Fixation ◽  
Primary Method ◽  
Dipolar Molecules ◽  
Wide Range ◽  
Time Required ◽  
Cryostat Sections

Microwaves (MW) are electromagnetic waves which are commonly generated at a frequency of 2.45 GHz. When dipolar molecules such as water, the polar side chains of proteins and other molecules with an uneven distribution of electrical charge are exposed to such non-ionizing radiation, they oscillate through 180° at a rate of 2,450 million cycles/s. This rapid kinetic movement results in accelerated chemical reactions and produces instantaneous heat. MWs have recently been applied to a wide range of procedures for light microscopy. MWs generated by domestic ovens have been used as a primary method of tissue fixation, it has been applied to the various stages of tissue processing as well as to a wide variety of staining procedures. This use of MWs has not only resulted in drastic reductions in the time required for tissue fixation, processing and staining, but have also produced better cytologic images in cryostat sections, and more importantly, have resulted in better preservation of cellular antigens.

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