%0 Generic %1 sironi2013relativistic %A Sironi, Lorenzo %A Giannios, Dimitrios %D 2013 %K blazars instability plasma tev %T Relativistic Pair Beams from TeV Blazars: A Source of Reprocessed GeV Emission rather than IGM Heating %U http://arxiv.org/abs/1312.4538 %X The interaction of TeV photons from blazars with the extragalactic background light produces a relativistic beam of electron-positron pairs streaming through the intergalactic medium (IGM). The fate of the beam energy is uncertain. By means of two- and three-dimensional particle-in-cell simulations, we study the non-linear evolution of dilute ultra-relativistic pair beams propagating through the IGM. We explore a wide range of beam Lorentz factors gamma_b>>1 and beam-to-plasma density ratios alpha<<1, so that our results can be extrapolated to the extreme parameters of blazar-induced beams (gamma_b~10^6 and alpha~10^(-15), for the most powerful blazars). For cold beams, we show that the oblique instability governs the early stages of evolution, but its exponential growth terminates - due to self-heating of the beam in the transverse direction - when only a negligible fraction ~(alpha/gamma_b)^(1/3)~10^(-7) of the beam energy has been transferred to the IGM plasma. Further relaxation of the beam proceeds through quasi-longitudinal modes, until the momentum dispersion in the direction of propagation saturates at DeltaP_b,parallel/gamma_b m_e c ~ 0.2. This corresponds to a fraction ~10% of the beam energy being ultimately transferred to the IGM plasma, irrespective of gamma_b or alpha. If the initial dispersion in beam momentum satisfies DeltaP_b,parallel/gamma_b m_e c > 0.2 (as typically expected for blazar-induced beams), the fraction of beam energy deposited into the IGM is much smaller than ~10%. It follows that at least ~90% of the beam energy is still available to power the GeV emission produced by inverse Compton up-scattering of the Cosmic Microwave Background by the beam pairs.

@misc{sironi2013relativistic, abstract = {The interaction of TeV photons from blazars with the extragalactic background light produces a relativistic beam of electron-positron pairs streaming through the intergalactic medium (IGM). The fate of the beam energy is uncertain. By means of two- and three-dimensional particle-in-cell simulations, we study the non-linear evolution of dilute ultra-relativistic pair beams propagating through the IGM. We explore a wide range of beam Lorentz factors gamma_b>>1 and beam-to-plasma density ratios alpha<<1, so that our results can be extrapolated to the extreme parameters of blazar-induced beams (gamma_b~10^6 and alpha~10^(-15), for the most powerful blazars). For cold beams, we show that the oblique instability governs the early stages of evolution, but its exponential growth terminates - due to self-heating of the beam in the transverse direction - when only a negligible fraction ~(alpha/gamma_b)^(1/3)~10^(-7) of the beam energy has been transferred to the IGM plasma. Further relaxation of the beam proceeds through quasi-longitudinal modes, until the momentum dispersion in the direction of propagation saturates at DeltaP_{b,parallel}/gamma_b m_e c ~ 0.2. This corresponds to a fraction ~10% of the beam energy being ultimately transferred to the IGM plasma, irrespective of gamma_b or alpha. If the initial dispersion in beam momentum satisfies DeltaP_{b,parallel}/gamma_b m_e c > 0.2 (as typically expected for blazar-induced beams), the fraction of beam energy deposited into the IGM is much smaller than ~10%. It follows that at least ~90% of the beam energy is still available to power the GeV emission produced by inverse Compton up-scattering of the Cosmic Microwave Background by the beam pairs.}, added-at = {2013-12-18T09:04:41.000+0100}, author = {Sironi, Lorenzo and Giannios, Dimitrios}, biburl = {https://www.bibsonomy.org/bibtex/29eaee754edfa66961ae57a75d25fb298/miki}, description = {[1312.4538] Relativistic Pair Beams from TeV Blazars: A Source of Reprocessed GeV Emission rather than IGM Heating}, interhash = {c7f2e5f7dc70a12d59e83717bb18a396}, intrahash = {9eaee754edfa66961ae57a75d25fb298}, keywords = {blazars instability plasma tev}, note = {cite arxiv:1312.4538Comment: 18 pages, 8 figures, submitted to ApJ}, timestamp = {2013-12-18T09:04:41.000+0100}, title = {Relativistic Pair Beams from TeV Blazars: A Source of Reprocessed GeV Emission rather than IGM Heating}, url = {http://arxiv.org/abs/1312.4538}, year = 2013 }