Magnetically driven coupling in relativistic radiation-mediated shocks

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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


The radiation drag in photon-rich environments of cosmic explosions can seed kinetic instabilities by inducing velocity spreads between relativistically streaming plasma components. Such microturbulence is likely imprinted on the breakout signals of radiation-mediated shocks. However, large-scale, transverse magnetic fields in the deceleration region of the shock transition can suppress the dominant kinetic instabilities by preventing the development of velocity separations between electron-positron pairs and a heavy ion species. We use a 1D five-fluid radiative transfer code to generate self-consistent profiles of the radiation drag force and plasma composition in the deceleration region. For increasing magnetization, our models predict rapidly growing pair multiplicities and a substantial radiative drag developing self-similarly throughout the deceleration region. We extract the critical magnetization parameter σc, determining the limiting magnetic field strength at which a three-species plasma can develop kinetic instabilities before reaching the isotropized downstream. For a relativistic, single ion plasma drifting with γu = 10 in the upstream of a relativistic radiation-mediated shock, we find the threshold σc ≈ 10-7 for the onset of microturbulence. Suppression of plasma instabilities in the case of multi-ion composition would likely require much higher values of σc. Identifying high-energy signatures of microturbulence in shock breakout signals and combining them with the magnetization limits provided in this work will allow a deeper understanding of the magnetic environment of cosmic explosions like supernovae, gamma-ray bursts, and neutron star binary mergers.

Original languageEnglish
Pages (from-to)6126-6137
Number of pages12
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - 1 Mar 2023


FundersFunder number
Multimessenger Plasma Physics CenterNIFS22KIST020, AST-1814708
United States Department of Energy Fusion Energy Sciences
National Science FoundationAST- 1909458
National Aeronautics and Space Administration80NSSC18K1099, PHY-2206607
Israel Science Foundation1995/21
Tel Aviv University


    • instabilities
    • methods: analytical
    • methods: numerical
    • plasmas
    • radiation mechanisms: general
    • shock waves


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