scholarly journals Radiation forces constrain the FRB mechanism

2020 ◽  
Vol 494 (1) ◽  
pp. 1217-1228 ◽  
Author(s):  
Pawan Kumar ◽  
Wenbin Lu
Keyword(s):  
Shock Front ◽  
Cyclotron Frequency ◽  
Generation Process ◽  
Frequency Wave ◽  
Relativistic Shocks ◽  
Radiation Forces ◽  
Fast Radio Burst ◽  
Photon Generation ◽  
Efficiency Consideration ◽  
Frame Duration

ABSTRACT We provide constraints on fast radio burst (FRB) models by careful considerations of radiation forces associated with these powerful transients. We find that the induced Compton scatterings of the coherent radiation by electrons/positrons accelerate particles to very large Lorentz factors (LFs) in and around the source of this radiation. This severely restricts those models for FRBs that invoke relativistic shocks and maser-type instabilities at distances less than about 1013 cm of the neutron star. Radiation travelling upstream, in these models, forces particles to move away from the shock with an LF larger than the LF of the shock front. This suspends the photon generation process after it has been operating for less than ∼0.1 ms (observer frame duration). We show that masers operating in shocks at distances larger than 1013 cm cannot simultaneously account for the burst duration of 1 ms or more and the observed ∼GHz frequencies of FRBs without requiring an excessive energy budget (>1046 erg); the energy is not calculated by imposing any efficiency consideration, or other details, for the maser mechanism, but is entirely the result of ensuring that particle acceleration by induced Compton forces upstream of the shock front does not choke off the maser process. For the source to operate more or less continuously for a few ms, it should be embedded in a strong magnetic field – cyclotron frequency ≫ wave frequency – so that radiation forces do not disperse the plasma and shut off the engine.

scholarly journals Optical Frequency Down-Conversion With Bandwidth Compression Based on Counter-Propagating Phase Matching

2021 ◽  
Vol 9 ◽  
Author(s):  
Dong-Jie Guo ◽  
Ran Yang ◽  
Yi-Chen Liu ◽  
Jia-Chen Duan ◽  
Zhenda Xie ◽  
...  
Keyword(s):  
Transfer Function ◽  
Large Scale ◽  
Difference Frequency Generation ◽  
Phase Matching ◽  
Generation Process ◽  
Periodically Poled ◽  
Central Wavelength ◽  
Bandwidth Compression ◽  
Photon Generation ◽  
Down Conversion

Optical quantum network plays an important role in large scale quantum communication. However, different components for photon generation, transmission, storage and manipulation in network usually cannot interact directly due to the wavelength and bandwidth differences, and thus interfaces are needed to overcome such problems. We propose an optical interface for frequency down-conversion and bandwidth compression based on the counter-propagating quasi-phase-matching difference frequency generation process in the periodically-poled lithium niobate on insulator waveguide. We prove that a separable spectral transfer function can be obtained only by choosing proper pump bandwidth, thus relaxing the limitation of material, dispersion, and working wavelength as a result of the counter-propagation phase-matching configuration. With numerical simulations, we show that our design results in a nearly separable transfer function with the Schmidt number very close to 1. With proper pump bandwidth, an photon at central wavelength of 550 nm with a bandwidth ranging from 50 GHz to 5 THz can be converted to a photon at central wavelength of 1,545 nm with a much narrower bandwidth of 33 GHz.

Nonlinear waves and shocks in relativistic two-fluid hydrodynamics

2012 ◽  
Vol 78 (3) ◽  
pp. 295-302 ◽  
Author(s):  
L. HAIM ◽  
M. GEDALIN ◽  
A. SPITKOVSKY ◽  
V. KRASNOSELSKIKH ◽  
M. BALIKHIN
Keyword(s):  
Energy Density ◽  
Shock Front ◽  
Magnetic Energy ◽  
Ambient Medium ◽  
Nonlinear Effects ◽  
Magnetic Energy Density ◽  
Fluid Analysis ◽  
Relativistic Shocks ◽  
Wide Range ◽  
Two Fluid

AbstractRelativistic shocks are present in a number of objects where violent processes are accompanied by relativistic outflows of plasma. The magnetization parameter σ = B2/4πnmc2 of the ambient medium varies in wide range. Shocks with low σ are expected to substantially enhance the magnetic fields in the shock front. In non-relativistic shocks the magnetic compression is limited by nonlinear effects related to the deceleration of flow. Two-fluid analysis of perpendicular relativistic shocks shows that the nonlinearities are suppressed for σ≪1 and the magnetic field reaches nearly equipartition values when the magnetic energy density is of the order of the ion energy density, Beq2 ~ 4πnmic2γ. A large cross-shock potential eφ/mic2γ0 ~ B2/Beq2 develops across the electron–ion shock front. This potential is responsible for electron energization.

scholarly journals Two-stream instabilities from the lower-hybrid frequency to the electron cyclotron frequency: application to the front of quasi-perpendicular shocks

2017 ◽  
Vol 35 (5) ◽  
pp. 1093-1112 ◽  
Author(s):  
Laurent Muschietti ◽  
Bertrand Lembège
Keyword(s):  
Shock Front ◽  
Cyclotron Frequency ◽  
Ion Beam ◽  
Wide Frequency Range ◽  
Electron Cyclotron ◽  
Lower Hybrid ◽  
Bernstein Waves ◽  
Synthetic View ◽  
Drift Instability ◽  
The Waves

Abstract. Quasi-perpendicular supercritical shocks are characterized by the presence of a magnetic foot due to the accumulation of a fraction of the incoming ions that is reflected by the shock front. There, three different plasma populations coexist (incoming ion core, reflected ion beam, electrons) and can excite various two-stream instabilities (TSIs) owing to their relative drifts. These instabilities represent local sources of turbulence with a wide frequency range extending from the lower hybrid to the electron cyclotron. Their linear features are analyzed by means of both a dispersion study and numerical PIC simulations. Three main types of TSI and correspondingly excited waves are identified: i. Oblique whistlers due to the (so-called fast) relative drift between reflected ions/electrons; the waves propagate toward upstream away from the shock front at a strongly oblique angle (θ ∼ 50°) to the ambient magnetic field Bo, have frequencies a few times the lower hybrid, and have wavelengths a fraction of the ion inertia length c∕ωpi. ii. Quasi-perpendicular whistlers due to the (so-called slow) relative drift between incoming ions/electrons; the waves propagate toward the shock ramp at an angle θ a few degrees off 90°, have frequencies around the lower hybrid, and have wavelengths several times the electron inertia length c∕ωpe. iii. Extended Bernstein waves which also propagate in the quasi-perpendicular domain, yet are due to the (so-called fast) relative drift between reflected ions/electrons; the instability is an extension of the electron cyclotron drift instability (normally strictly perpendicular and electrostatic) and produces waves with a magnetic component which have frequencies close to the electron cyclotron as well as wavelengths close to the electron gyroradius and which propagate toward upstream. Present results are compared with previous works in order to stress some features not previously analyzed and to define a more synthetic view of these TSIs.

scholarly journals Particle Acceleration in Gamma-Ray Bursts

2005 ◽  
Vol 192 ◽  
pp. 475-482
Author(s):  
J.G. Kirk
Keyword(s):  
Magnetic Field ◽  
Particle Acceleration ◽  
Shock Front ◽  
Gamma Ray ◽  
Crab Nebula ◽  
High Energy ◽  
Gamma Ray Bursts ◽  
Magnetic Field Generation ◽  
Relativistic Shocks ◽  
The Crab Nebula

SummarySimple kinematic theories of particle acceleration at relativistic shocks lead to the prediction of a high-energy spectral index of −1.1 for the energy flux of synchrotron photons. However, several effects can change this picture. In this paper I discuss the effect of magnetic field generation at the shock front and, by analogy with the Crab Nebula, suggest that an intrinsic break in the injection spectrum should be expected where the electron gyro radius is comparable to that of protons thermalized by the shock.

Optimization of Beat Frequency Plasma Heating near the Electron Cyclotron Frequency

1974 ◽  
Vol 52 (22) ◽  
pp. 2223-2227 ◽  
Author(s):  
C. E. Capjack ◽  
C. R. James
Keyword(s):  
Cyclotron Frequency ◽  
Plasma Heating ◽  
Beat Frequency ◽  
Laser Beams ◽  
Plasma Power ◽  
Electron Current ◽  
Frequency Wave ◽  
Parametric Dependence ◽  
Frequency Plasma ◽  
Nonlinear Mixing

The plasma power absorbed from a beat frequency wave generated through the nonlinear mixing of two laser beams may be optimized by the utilization of an electron current resonance. The parametric dependence of the plasma power absorption near an electron resonance is examined together with experimental considerations for the case where CO2 lasers are used.

scholarly journals Power-Law Spectra from Fermi Acceleration at Relativistic Shocks

1989 ◽  
Vol 134 ◽  
pp. 211-212
Author(s):  
J. G. Kirk
Keyword(s):  
Shock Front ◽  
Power Law ◽  
Hot Spots ◽  
Pitch Angle ◽  
Average Energy ◽  
Acceleration Process ◽  
Fermi Acceleration ◽  
Physical Reason ◽  
Relativistic Shocks ◽  
Angle Scattering

The theory of diffusive acceleration at shock fronts, which applies only if the fluid speed is nonrelativistic, yields a simple formula for the power-law index s of accelerated particles: s = 3r/(r – 1), where r is the compression ratio of the shock front. Although the acceleration process depends on there being effective pitch-angle scattering of the particles in both the upstream and downstream regions, no property associated with this process appears in the formula. Unfortunately, if the velocity of the fluid through the shock front is relativistic, as seems to be the case in the central engines of AGN's, and also in some hot-spots in the outerparts of their jets, this attractive property ceases to hold. To find the index s, it becomes necessary to develop specific models describing the scattering process. The physical reason for this is that the particle distribution close to a relativistic shock is anisotropic. The exact type of anisotropy depends on the properties of the pitch angle scattering and determines both the average energy gain per shock crossing, as well as the probability of escape downstream. In this paper, results are presented for the pitch angle diffusion resulting from scattering in a weakly turbulent plasma with a Kolmogorov spectrum of Alfvén waves moving parallel and antiparallel to the magnetic field. This kind of spectrum has been employed in nonrelativistic models of hot spots [1]. However, the results obtained tend not to vary too dramatically as a function of the turbulence spectrum, being less than about 0.2 in the resulting s (0.1 in the predicted synchroton spectral index) for turbulence spectra between k−1 and k−2 [3].

Dynamical Casimir effect and photon generation process in time dependent quantum graph

2020 ◽  
Author(s):  
Ekaterina S. Trifanova ◽  
Alexander I. Trifanov ◽  
Igor S. Lobanov ◽  
Dmitrii S. Nikiforov ◽  
Igor Y. Popov
Keyword(s):  
Casimir Effect ◽  
Quantum Graph ◽  
Time Dependent ◽  
Generation Process ◽  
Dynamical Casimir Effect ◽  
Photon Generation

scholarly journals Correction of complex nonlinear signal response from a pixel array detector

2015 ◽  
Vol 22 (3) ◽  
pp. 584-591 ◽  
Author(s):  
Tim Brandt van Driel ◽  
Sven Herrmann ◽  
Gabriella Carini ◽  
Martin Meedom Nielsen ◽  
Henrik Till Lemke
Keyword(s):  
Single Pulse ◽  
Array Detector ◽  
Light Sources ◽  
Generation Process ◽  
Pulse Detection ◽  
Area Detector ◽  
Signal Distortions ◽  
Signal Changes ◽  
Nonlinear Signal ◽  
Photon Generation

The pulsed free-electron laser light sources represent a new challenge to photon area detectors due to the intrinsic spontaneous X-ray photon generation process that makes single-pulse detection necessary. Intensity fluctuations up to 100% between individual pulses lead to high linearity requirements in order to distinguish small signal changes. In real detectors, signal distortions as a function of the intensity distribution on the entire detector can occur. Here a robust method to correct this nonlinear response in an area detector is presented for the case of exposures to similar signals. The method is tested for the case of diffuse scattering from liquids where relevant sub-1% signal changes appear on the same order as artifacts induced by the detector electronics.

Radio‐frequency wave interchange stability experiments below the ion cyclotron frequency

1989 ◽  
Vol 1 (8) ◽  
pp. 1692-1701 ◽  
Author(s):  
J. J. Browning ◽  
N. Hershkowitz ◽  
T. Intrator ◽  
R. Majeski ◽  
S. Meassick
Keyword(s):  
Radio Frequency ◽  
Cyclotron Frequency ◽  
Frequency Wave ◽  
Ion Cyclotron ◽  
Radio Frequency Wave

Investigation of shock-wave deformation history from recovered structure

1986 ◽  
Vol 44 ◽  
pp. 434-435
Author(s):  
M.A. Mogilevsky ◽  
L.S. Bushnev
Keyword(s):  
Shock Wave ◽  
Plastic Deformation ◽  
Dislocation Density ◽  
Shock Waves ◽  
Shock Front ◽  
Single Crystals ◽  
Residual Deformation ◽  
Deformation Structure ◽  
Deformation History ◽  
Deformation Velocity

Single crystals of Al were loaded by 15 to 40 GPa shock waves at 77 K with a pulse duration of 1.0 to 0.5 μs and a residual deformation of ∼1%. The analysis of deformation structure peculiarities allows the deformation history to be re-established.After a 20 to 40 GPa loading the dislocation density in the recovered samples was about 1010 cm-2. By measuring the thickness of the 40 GPa shock front in Al, a plastic deformation velocity of 1.07 x 108 s-1 is obtained, from where the moving dislocation density at the front is 7 x 1010 cm-2. A very small part of dislocations moves during the whole time of compression, i.e. a total dislocation density at the front must be in excess of this value by one or two orders. Consequently, due to extremely high stresses, at the front there exists a very unstable structure which is rearranged later with a noticeable decrease in dislocation density.

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