Relativistic Streaming Effects on Electromagnetic Instability in Magnetoplasmas

The electromagnetic waves propagating transverse to the direction of streaming of the contrastreaming plasmas in the presence of a uniform magnetic field are investigated. For electron plasmas these waves become unstable only for some bounded values of the streaming velocity U₀, namely, Uₘᵢₙ<U₀<Uₘₐₓ. For relativistic streaming velocities, the electron thermal effects are destabilizing whereas for nonrelativistic streaming these are stabilizing unless c²k²ωₚₑ²<1/3 and k²Vₜₑ²Ωₑ²1 (k being the characteristic wave number, Vₜₑ the electron thermal velocity, Ωₑ the electron cyclotron frequency, and ωₚₑ the electron plasma frequency). The magnetic field however reduces the region of instability no matter what the streaming velocity is. The effect of nonrelativistic-ion streaming is destabilizing while that of the ion temperature is stabilizing. In the presence of a strong magnetic field, the effect of relativistic-ion streaming is also stabilizing.