Abstract
The attenuation of TeV γ-rays from distant blazars by the extragalactic background light (EBL) produces relativistic electron-positron pair beams. It has been shown by Broderick et. al. (2012) and Schlickeiser et. al (2012) that a pair beam traversing the intergalactic medium is unstable to linear two-stream instabilities of both electrostatic and electromagnetic nature. While for strong blazars all free pair energy is dissipated in heating the intergalactic medium and a potential electromagnetic cascade via inverse-Compton scattering with the cosmic microwave background is suppressed, we investigate the case of weak blazars where the back reaction of generated electrostatic turbulence leads to a plateauing of the electron energy spectrum. In the ultra-relativistic Thomson limit we analytically calculate the inverse-Compton spectral energy distribution for both an unplateaued and a plateaued beam scenario, showing a peak reduction factor of Rpeak ≈ 0.345. This is consistent with the FERMI non-measurements of a GeV excess in the spectrum of EBL attenuated TeV blazars. Claims on the lower bound of the intergalactic magnetic field strengths, made by several authors neglecting plasma effects, are thus put into question.
Highlights
The absorption of the TeV γ-ray component from distant blazars is based on the production of e± particle beams in double photon collisions with the extragalactic background light (EBL)
On the one hand the existence of a strong intergalactic magnetic field (IGMF) could deflect the charged pairs leading to intensity reduced extended emission and possible time lags in non-stationary situations
On the other hand it has been shown that the pair beam traversing the intergalactic medium (IGM) is subject to two-stream like instabilities of electrostatic and electromagnetic nature.[8,9,10]
Summary
The absorption of the TeV γ-ray component from distant blazars is based on the production of e± particle beams in double photon collisions with the extragalactic background light (EBL). Inverse-Compton scattering of these relativistic particles with the cosmic microwave background (CMB) leads to still energetic photons up to the GeV regime These photons are energetic enough to overcome the threshold for pair production, an electromagnetic cascade evolves. On the one hand the existence of a strong intergalactic magnetic field (IGMF) could deflect the charged pairs leading to intensity reduced extended emission and possible time lags in non-stationary situations Presuming this scenarios, several authors derived constrains on the lower bound of the IGMF strengths and its correlation lengths.[1,2,3,4,5,6,7] On the other hand it has been shown that the pair beam traversing the intergalactic medium (IGM) is subject to two-stream like instabilities of electrostatic and electromagnetic nature.[8,9,10] As has been shown in Ref. 9 depending on the blazar VHE luminosity either, all free pair energy is dissipated via modulation instability in heating the IGM, or half of the beam energy is transferred into electrostatic and electromagnetic fluctuations. We will calculate the inverse-Compton flux resulting from both unplateaued and plateaued electron beams traversing the CMB to investigate the flux reduction due to beam plasma effects
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
