%AVanthieghem, A.%AMahlmann, J.%ALevinson, A.%APhilippov, A.%ANakar, E.%AFiuza, F.%BJournal Name: Monthly Notices of the Royal Astronomical Society; Journal Volume: 511; Journal Issue: 2; Related Information: CHORUS Timestamp: 2023-02-11 20:01:15 %D2022%IOxford University Press %JJournal Name: Monthly Notices of the Royal Astronomical Society; Journal Volume: 511; Journal Issue: 2; Related Information: CHORUS Timestamp: 2023-02-11 20:01:15 %K %MOSTI ID: 10362907 %PMedium: X %TThe role of plasma instabilities in relativistic radiation-mediated shocks: stability analysis and particle-in-cell simulations %XABSTRACT

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.

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