Relaxation of Blazar Induced Pair Beams in Cosmic Voids
- Working Paper
The stability properties of a low density ultra relativistic pair beam produced in the intergalactic medium by multi-TeV gamma-ray photons from blazars are analyzed. The problem is relevant for probes of magnetic field in cosmic voids through gamma-ray observations. In addition, dissipation of such beams could affect considerably the thermal history of the intergalactic medium and structure formation. We use a Monte Carlo method to quantify the shower properties, in particular the bulk Lorentz factor and the angular spread of the beam, as a function of distance from the blazar. We find that the fastest growing modes, like any perturbation mode with even a very modest component perpendicular to the beam direction, requires a kinetic treatment. Combined with the effect of non-linear Landau damping, which suppresses the growth of plasma oscillations, the beam relaxation timescale is found typically longer than a Hubble time. Finally, density inhomogeneities associated with cosmic structure induce severe loss of resonance between the beam particles and plasma oscillations, strongly inhibiting their growth. We conclude that relativistic pair beams produced by blazars in the intergalactic medium are stable on timescales much longer compared to the electromagnetic cascade's. There appears to be no effect of pair-beams on the intergalactic medium Show more
Pages / Article No.
Organisational unit03613 - Lilly, Simon / Lilly, Simon
NotesSubmitted 8 August 2012.
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