Kinetic theory for radiation interacting with sound waves in ultrarelativistic pair plasmas

Abstract

A kinetic theory for radiation interacting with sound waves in an ultrarelativistic electron-positron plasma is developed. It is shown that the effect of a spatial spectral broadening of the electromagnetic pulse is to introduce a reduction of the growth rates for the decay and modulational instabilities. Such spectral broadening could be due to a finite pulse coherence length, or through the use of random phase filters, and would stabilize the propagation of electromagnetic pulses.The physics of electron-positron plasmas is important for understanding the pulsar environments [1, 2] and laboratory plasmas irradiated by intense lasers [3,4], where quantum field effects come into play [5]. Pair plasmas are also believed to be important in the early universe, in supernova remnants and active galactic nuclei, and in gamma-ray bursts [6,7].A pair plasma can be created in these environments by collisions between strongly accelerated particles [8]. There is also a possibility of pair creation via high-energy curvature radiation photons in the vicinity of strongly magnetized astrophysical objects, triggered by charged particles streaming along the curved magnetic field [9]. This results in large quantities of positrons produced close to pulsar polar caps [10,11]. In laboratory environments, laser experiments with focal spot intensities exceeding 10 20 W/cm 2 have demonstrated the production of MeV electrons and evidence of positrons via laser multiphoton-gamma photon interactions [12,13] as well as via electron collisions [14,15].When the intensity of the radiation is increased, the pair plasma particles attain rela- * Electronic address: mattias.marklund@physics.umu.se; Also at