The role of resonant plasma instabilities in the evolution of blazar-induced pair beams

Abstract

The fate of relativistic pair beams produced in the intergalactic medium by very-high energy emission from blazars remains controversial in the literature. The possible role of resonance beam plasma instability has been studied both analytically and numerically but no consensus has been reached. In this paper, we thoroughly analyze the development of this type of instability. This analysis takes into account that a highly relativistic beam loses energy only due to interactions with the plasma waves propagating within the opening angle of the beam (we call them parallel waves), whereas excitation of oblique waves results merely in an angular spreading of the beam, which reduces the instability growth rate. For parallel waves, the growth rate is a few times larger than for oblique ones, so they grow faster than oblique waves and drain energy from the beam before it expands. However, the specific property of extragalactic beams is that they are extraordinarily narrow; the opening angle is only Δθ ∼ 10−6 − 10−5. In this case, the width of the resonance for parallel waves, ∝Δθ2, is too small for them to grow in realistic conditions. We perform both analytical estimates and numerical simulations in the quasilinear regime. These show that for extragalactic beams, the growth of the waves is incapable of taking a significant portion of the beam’s energy. This type of instability could at best lead to an expansion of the beam by some factor but the beam’s energy remains nearly intact.

Suppression of the TeV pair-beam plasma instability by a tangled weak intergalactic magnetic field

“…Cosmological simulations including this heating process can successfully reproduce the observed IGM temperature and the effective optical depth as a function of redshift as well with several other observations (Puchwein et al 2012). Perry & Lyubarsky (2021) argued otherwise, namely that the back reaction of the unstable waves on the pair beam particles distribution moderately scatters the beam particles and does not impose a significant energy loss. We do not discuss the particulars of the nonlinear feedback here and leave this issue for future studies.…”

Quantum gravity phenomenology at the dawn of the multi-messenger era -- A review

“…Nevertheless, the role played by IGMFs on the cascades has been recently questioned in a number of works [965,966], which claim that plasma instabilities arising due to the back-reaction of the intergalactic medium on the electrons of the cascade could effectively halt the production of high-energy secondary gamma rays, cooling down the electrons before they can up-scatter background photons. Nevertheless, while this effect might actually play a substantial role, there are indications that this process does not completely quench the development of the cascades [967,968]. For a more detailed discussion, see Ref.…”

The Gamma-ray Window to Intergalactic Magnetism

“…Even if one accepts this assumption, it is not clear which kind of instability could be dominant. In fact, the modulation [289,[291][292][293], oblique [288,294,295], kinetic [296], and longitudinal [297] instabilities, as well as non-linear Landau Damping [298] have been considered in the literature. On the other hand, Ref.…”