Ordinary-Mode Electromagnetic Instability in Colliding Plasma Streams

Abstract

The ins tability of the electromagnetic linearly polarized mode propagating perpendicular to the magnetic field is studied for a system composed of two colliding plasma streams, in each of which both the electrons and the ions are streaming at the same velocity . Based on the linearized Vlasov-Maxwel 1 equations and allowing for anisotropic temperatures, it is found that in the presence of streaming ions the instability can occur in very low-P plasmas . The higher the values of p, the streaming velocity, and the temperature ratios T(~ff/T~a nd T~/T J f, the more the plasma is susceptible to the electromagnetic instability . The ratio T" f /T, ) has negligible influence, except when the streaming velocity is smaller than the ion the rma 1 speed .It is found that for p values of order unity, the streaming ions, while greatly enlarging the range of unstable wave numbe rs, contribute negligibly to the maximum growth rate, which is typically of the order of the electron cyclotron frequency . A comparison with the growth rates of the electros tatic two-stream instability is made .

Cumulative effect of the Weibel-type instabilities in symmetric counterstreaming plasmas with kappa anisotropies

“…Further investigations have been carried out in order to examine these instabilities in a magnetized counterstreaming plasma with a bi-Maxwellian electron temperature anisotropy [14,15,16]. As expected, the presence of a dc magnetic field in the streaming direction inhibits the Weibel-type instabilities [8,17,18].…”

Evidence for monochromatic unstable Weibel modes in asymmetric counterstreaming pair plasmas

“…The excitation of Weibel modes in Maxwellian plasmas that are counterstreaming along a homogeneous magnetic field has been investigated analytically Schlickeiser 2005b, 2006;Bornatici and Lee 1970;Lee and Armstrong 1971), where the excitation of purely growing Weibel modes has been confirmed and the growth rates have been calculated numerically. Simulations of counterstreaming plasma distributions show the excitation of electrostatic shock waves (Haruki and Sakai 2003) and highfrequency electromagnetic waves (Saito and Sakai 2004) and have, furthermore, confirmed the analytically calculated growth rates of the ordinary-wave mode (Tautz and Sakai 2007) propagates perpendicularly to the background magnetic field.…”

Constraints for the aperiodic O-mode streaming instability

“…In the presence of streams, propagating along the ordered magnetic field, the activity of this instability extends to low beta β < 1 states [2][3][4][9][10][11] (although the instability is inhibited by the magnetic field by limiting the range of unstable wavenumbers 1 ). Thus, for two symmetric counterstreams of electrons (subscript e) the conditions necessary for the O-mode instability are 9 β e, > 2/(1 + 2V 2 e /u 2 e, ) and A e < 1 + 2V 2 e /u 2 e, , where u e, = (2k B T e, /m e ) 1/2 is the electron thermal velocity in parallel direction, β e, = 8πnk B T e, /B 2 0 , and V e is the streaming velocity.…”