{
  "abstract": "Using analytic theory, radiative particle-in-cell (PIC) simulations, and fluid simulations, we show that relativistic, synchrotron-cooling, collisionless, high-$β$ pair plasmas filament into a two-phase medium. This process occurs through the interplay of the synchrotron cooling instability (SCI) with the synchrotron firehose instability (SFHI). One phase has high plasma~$β$ and is infested with small-scale firehose fluctuations, which scatter particles and pin the pressure anisotropy to the firehose-marginal level. The other phase has much lower~$β$, causing the suppression of firehose modes and thus allowing large pressure anisotropies. We propose a fluid model for this two-phase plasma, which we use to study the linear and nonlinear evolution of the SCI and SFHI, and to predict the emergence time of the two-phase structure.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2609.07793",
  "author_total": 5,
  "authors": [
    {
      "name": "Agnieszka Wierzchucka"
    },
    {
      "name": "Pablo J. Bilbao"
    },
    {
      "name": "Robert J. Ewart"
    },
    {
      "name": "Dmitri A. Uzdensky"
    },
    {
      "name": "Alexander A. Schekochihin"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/4bwndznk4j3ne.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2609.07793",
  "fulltext_url": null,
  "id": "4bwndznk4j3ne",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2609.07793",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "http://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.HE"
    ],
    [
      "arxiv",
      "physics.plasm-ph"
    ],
    [
      "openalex",
      "3106|Astrophysics and Cosmic Phenomena"
    ]
  ],
  "openalex": "W7212000078",
  "pdf_url": "https://arxiv.org/pdf/2609.07793",
  "pmcid": null,
  "pmid": null,
  "published": "2026-09-07",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/4bwndznk4j3ne.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:19:48Z",
      "native_id": "2609.07793",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2609.07793"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    },
    {
      "field": "physics",
      "origin": "arxiv:physics.plasm-ph",
      "subfield": "plasma"
    }
  ],
  "title": "Two-Phase Structure of Synchrotron-Cooling-Unstable Relativistic Plasma",
  "title_text": "Two-Phase Structure of Synchrotron-Cooling-Unstable Relativistic Plasma",
  "type": "preprint",
  "updated_at": "2026-10-30T12:19:48Z",
  "url": "https://research.draconitic.com/paper/4bwndznk4j3ne",
  "venue": "arXiv",
  "versions": []
}