{
  "abstract": "Plasmoids, or magnetic islands, dominate relativistic reconnection layers in kinetic simulations, yet the instability that creates them remains poorly understood. By tracking newborn islands in 2D particle-in-cell simulations of pair-plasma reconnection with magnetizations $0.1\\leσ_0\\le1000$, we show that plasmoids are seeded by a current-filamentation/Weibel instability driven by counter-streaming out-of-plane current carriers near primary x-lines. Measured growth rates are $\\sim0.1$ times the background plasma frequency and agree with linear theory evaluated on the simulated distributions. As inflowing plasma loads the sheet away from the x-line, the current is carried by more particles and their out-of-plane drift slows. The filamentation instability shuts off once this drift becomes comparable to the momentum spread in the outflow direction, which occurs at a distance $\\ell_{\\rm iso}\\proptoσ_0$ from the x-line. Because the unstable region extends farther at higher $σ_0$, our results account for the onset of plasmoid-dominated reconnection in the relativistic regime but predict that plasmoid formation is suppressed beyond $\\sim\\ell_{\\rm iso}$ from primary x-lines, even in ultra-relativistic reconnection. Particle acceleration, variability, and coherent radio emission attributed to plasmoid-dominated reconnection may therefore be confined to smaller regions than previously assumed.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2611.02126",
  "author_total": 2,
  "authors": [
    {
      "name": "Matthew Goodbred"
    },
    {
      "name": "Anatoly Spitkovsky"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/816f8mrmdmzx6.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2611.02126",
  "fulltext_url": null,
  "id": "816f8mrmdmzx6",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2611.02126",
  "language": null,
  "licence": "LicenseRef-arXiv-nonexclusive-1.0",
  "licence_label": "arXiv licence",
  "licence_source": "article",
  "licence_url": "http://arxiv.org/licenses/nonexclusive-distrib/1.0/",
  "metadata_licence": "CC0-1.0",
  "native_subjects": [
    [
      "arxiv",
      "astro-ph.HE"
    ],
    [
      "arxiv",
      "physics.plasm-ph"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2611.02126",
  "pmcid": null,
  "pmid": null,
  "published": "2026-11-01",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/816f8mrmdmzx6.ris",
  "sources": [
    {
      "first_seen": "2026-11-03T12:20:59Z",
      "native_id": "2611.02126",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2611.02126"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    },
    {
      "field": "physics",
      "origin": "arxiv:physics.plasm-ph",
      "subfield": "plasma"
    }
  ],
  "title": "The Birth of Plasmoids: Weibel-Driven Secondary Tearing and its Suppression in Relativistic Reconnection",
  "title_text": "The Birth of Plasmoids: Weibel-Driven Secondary Tearing and its Suppression in Relativistic Reconnection",
  "type": "preprint",
  "updated_at": "2026-11-05T15:20:18Z",
  "url": "https://research.draconitic.com/paper/816f8mrmdmzx6",
  "venue": "arXiv",
  "versions": []
}