Bunching Instability of Rotating Relativistic Electron Layers and Coherent Synchrotron Radiation
Abstract
We study the stability of a collisionless, relativistic, finite strength, cylindrical layer of charged particles (in our case electrons) in free space by solving the linearized VlasovMaxwell system of equations. This system is of interest to understanding the high brightness temperature coherent synchrotron radio emission of pulsars which cannot be explained by an incoherent radiation mechanism. Coherent synchrotron radiation has also been observed recently in bunch compressors used in particle accelerators where the collective emission of coherent synchrotron radiation can lead to a microwave instability. In our calculation we have to retain the retardation of the electric and magnetic fields. We use a rigid rotor equilibrium whose equilibrium layers have a thermal energy spread and therefore a finite radial thickness. In our model the electrons are considered to move either perpendicular or parallel to a external magnetic field interacting with their own selffields. A short azimuthal wavelength instability is found which causes a modulation of the charge and current densities which moves azimuthally at approximately the relativistic speed of the electrons. The instability arises from the negative effective mass for the azimuthal motion of the relativistic particles. The growth rate is found to be an increasing function of the azimuthal wavenumber, a decreasing function of the Lorentz factor and proportional to the square root of the total number of electrons. The growth rate decreases as the temperature decreases.
 Publication:

APS Division of Plasma Physics Meeting Abstracts
 Pub Date:
 October 2003
 Bibcode:
 2003APS..DPPUP1048S