The role of plasma instabilities in relativistic radiation-mediated shocks: Stability analysis and particle-in-cell simulations

A. Vanthieghem, J. F. Mahlmann, A. Levinson, A. Philippov, E. Nakar, F. Fiuza

Research output: Contribution to journalArticlepeer-review

Abstract

Relativistic radiation-mediated shocks are likely formed in prodigious cosmic explosions. The structure and emission of such shocks are regulated by copious production of electron-positron pairs inside the shock-transition layer. It has been pointed out recently that substantial abundance of positrons inside the shock leads to a velocity separation of the different plasma constituents, which is expected to induce a rapid growth of plasma instabilities. In this paper, we study the hierarchy of plasma microinstabilities growing in an electron-ion plasma loaded with pairs and subject to a radiation force. Linear stability analysis indicates that such a system is unstable to the growth of various plasma modes which ultimately become dominated by a current filamentation instability driven by the relative drift between the ions and the pairs. These results are validated by particle-in-cell simulations that further probe the non-linear regime of the instabilities, and the pair-ion coupling in the microturbulent electromagnetic field. Based on this analysis, we derive a reduced-transport equation for the particles via pitch-angle scattering in the microturbulence and demonstrate that it can couple the different species and lead to non-adiabatic compression via a Joule-like heating. The heating of the pairs and, conceivably, the formation of non-thermal distributions, arising from the microturbulence, can affect the observed shock-breakout signal in ways unaccounted for by current single-fluid models.

Original languageEnglish
Pages (from-to)3034-3045
Number of pages12
JournalMonthly Notices of the Royal Astronomical Society
Volume511
Issue number2
DOIs
StatePublished - 1 Apr 2022

Keywords

  • Instabilities
  • Methods: analytical
  • Methods: numerical
  • Plasmas
  • Radiation mechanisms: general
  • Shock waves

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