Wake field in electron–positron plasmas

1993 ◽  
Vol 50 (1) ◽  
pp. 79-84 ◽  
Author(s):  
K. Avinash ◽  
V. I. Berezhiani
Keyword(s):  
Quantitative Estimation ◽  
Galactic Nuclei ◽  
Pulsar Magnetosphere ◽  
Plasma Inhomogeneity ◽  
Pulsar Radio ◽  
Wake Field ◽  
Electron Bunches ◽  
Electron Positron ◽  
Photon Acceleration ◽  
Photon Motion

SummaryWe have studied the possibility of exciting a wake field in an electron–positron plasma by the injection of relativistic electron bunches. We have investigated the change in frequency of electronmagnetic radiation propagating through the resulting inhomogeneity. Our main conclusion is that it is not necessary to invoke a magnetic field in order to excite a wake field in an electron–positron plasma. As shown here, the necessary charge separation could come from the injection of energetic particle bunches. This mechanism of wake-field creation and subsequent particle/photon acceleration could operate in a pulsar magnetosphere, where particle bunches are extracted energetically from the pulsar surface. For example, pulsar radio emissions exhibit ultra-short intensity variations within individual pulses with time scales ranging from 1 μs to 1 ms (Cordes 1979). Several authors have proposed (Chian & Kennel 1983; Mofiz, De Angelis & Forlani 1985; Mikhailovskii, Onishchenko & Tatarinov 1985) that these pulsations can be explained as being due to soliton formation in the pulsar magnetosphere.We believe that these micropulsations can also be explained by modulation of the radiation caused by the wake field. In order to have a quantitative estimation, we need to take into account the effects of thermal motion of particles as well as plasma inhomogeneity, etc. The present results should also be useful for understanding nonolinear photon motion in cosmic plasmas, such as those found in the early universe and in active galactic nuclei (Tajima & Taniuti 1990).

scholarly journals Alfvén resonance absorption in electron-positron plasmas

2010 ◽  
Vol 6 (S274) ◽  
pp. 224-227 ◽  
Author(s):  
N. F. Cramer
Keyword(s):  
Mode Conversion ◽  
Alfven Wave ◽  
Pulsar Magnetosphere ◽  
Pulsar Radio ◽  
Inertial Alfvén Wave ◽  
Pair Plasma ◽  
Electron Positron ◽  
Normal Electron ◽  
The Magnetic Field ◽  
Pulsar Radio Emission

AbstractWaves propagating obliquely in a magnetized cold pair plasma experience an approximate resonance in the wavevector component perpendicular to the magnetic field, which is the analogue of the Alfvén resonance in normal electron-ion plasmas. Wave absorption at the resonance can take place via mode conversion to the analogue of the short wavelength inertial Alfvén wave. The Alfvén resonance could play a role in wave propagation in the pulsar magnetosphere leading to pulsar radio emission. Ducting of waves in strong plasma gradients may occur in the pulsar magnetosphere, which leads to the consideration of Alfvén surface waves, whose energy is concentrated in the region of strong gradients.

The Natural Wave Modes in a Pulsar Magnetosphere

1977 ◽  
Vol 3 (2) ◽  
pp. 120-122 ◽  
Author(s):  
D. B. Melrose ◽  
R. J. Stoneham
Keyword(s):  
Radio Emission ◽  
Pulsar Magnetosphere ◽  
Natural Wave ◽  
Pulsar Radio ◽  
Electron Positron ◽  
Polarization Characteristics ◽  
Pulsar Radio Emission ◽  
Wave Modes

Our purpose in this paper is to explore the properties of the natural wave modes of a relativistically streaming electron-positron gas and to apply the results to the interpretation of the polarization characteristics of pulsar radio emission.

scholarly journals Propagation Effects on Pulsar Radio Emission

2001 ◽  
Vol 18 (4) ◽  
pp. 400-406 ◽  
Author(s):  
Qinghuan Luo
Keyword(s):  
Radio Emission ◽  
Pulsar Magnetosphere ◽  
Pulsar Radio ◽  
Dispersion Effects ◽  
Electron Positron ◽  
Primary Particles ◽  
Propagation Effects ◽  
Plasma Dispersion ◽  
Pulsar Radio Emission ◽  
Relativistic Pair

AbstractPropagation effects on radio emission within the pulsar magnetosphere are discussed. Widely accepted pulsar models assume that a pulsar magnetosphere is populated with relativistic pair plasmas produced through electron–positron cascades by accelerated primary particles above the polar cap. Any radio emission produced well inside the light cylinder (the radius at which the rotation speed equals c) must propagate through the magnetospheric plasma and be subject to plasma dispersion effects such as refraction and absorption. The observed pulse profiles should contain some features that reflect the influence of the intervening plasma. I discuss particularly the absorption effect due to cyclotron resonance and its possible observational consequences.

scholarly journals Beam instabilities in a magnetized pair plasma

1999 ◽  
Vol 62 (1) ◽  
pp. 65-86 ◽  
Author(s):  
MAXIM LYUTIKOV
Keyword(s):  
Growth Rates ◽  
Particle Interaction ◽  
Kinetic Regime ◽  
Pulsar Magnetosphere ◽  
Pair Plasma ◽  
Electron Positron ◽  
Pulsar Radiation ◽  
Radiation Generation ◽  
Field Lines ◽  
Beam Instabilities

Beam instabilities in the strongly magnetized electron–positron plasma of a pulsar magnetosphere are considered. We analyse the resonance conditions and estimate the growth rates of the Cherenkov and cyclotron instabilities of the ordinary (O), extraordinary (X) and Alfvén modes in two limiting regimes: kinetic and hydrodynamic. The importance of the different instabilities as a source of coherent pulsar radiation generation is then estimated, taking into account the angular dependence of the growth rates and the limitations on the length of the coherent wave–particle interaction imposed by the curvature of the magnetic field lines. We conclude that in the pulsar magnetosphere, Cherenkov-type instabilities occur in the hydrodynamic regime, while cyclotron-type instabilities occur in the kinetic regime. We argue that electromagnetic cyclotron-type instabilities on the X, O and probably Alfvén waves are more likely to develop in the pulsar magnetosphere.

scholarly journals Coupling Effects in Multistage Laser Wake-field Acceleration of Electrons

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Zhan Jin ◽  
Hirotaka Nakamura ◽  
Naveen Pathak ◽  
Yasuo Sakai ◽  
Alexei Zhidkov ◽  
...  
Keyword(s):  
Laser Pulse ◽  
Electron Beams ◽  
High Energy ◽  
Long Distance ◽  
Plasma Cathode ◽  
Particle In Cell ◽  
Wake Field ◽  
Spatial Coupling ◽  
Electron Bunches ◽  
A Charge

AbstractStaging laser wake-field acceleration is considered to be a necessary technique for developing full-optical jitter-free high energy electron accelerators. Splitting of the acceleration length into several technical parts and with independent laser drivers allows not only the generation of stable, reproducible acceleration fields but also overcoming the dephasing length while maintaining an overall high acceleration gradient and a compact footprint. Temporal and spatial coupling of pre-accelerated electron bunches for their injection in the acceleration phase of a successive laser pulse wake field is the key part of the staging laser-driven acceleration. Here, characterization of the coupling is performed with a dense, stable, narrow energy band of <3% and energy-selectable electron beams with a charge of ~1.6 pC and energy of ~10 MeV generated from a laser plasma cathode. Cumulative focusing of electron bunches in a low-density preplasma, exhibiting the Budker–Bennett effect, is shown to result in the efficient injection of electrons, even with a long distance between the injector and the booster in the laser pulse wake. The measured characteristics of electron beams modified by the booster wake field agree well with those obtained by multidimensional particle-in-cell simulations.

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