{
  "abstract": "Relativistic jets are observed in some accreting black-hole systems but not others. In X-ray binaries, jet production is closely associated with geometrically thicker accretion states, suggesting that disk thickness may influence the conditions for jet launching. We investigate this connection using three-dimensional GRMHD simulations of disks with $h/r=0.1$--$0.3$, initialized with a toroidal magnetic field with plasma $β=5$. We find that the magnetorotational instability (MRI) generates large-scale poloidal fields through non-axisymmetric shearing waves, with an additional contribution from axisymmetric induction through stretching by channel-like modes. The resulting mean fields become progressively weaker as the disk becomes thinner. Because these fields regulate MRI turbulence, thinner disks exhibit weaker angular-momentum transport and accrete more slowly than the standard $v_{\\rm acc}\\propto(h/r)^2$ thin-disk scaling would predict. The magnetic-flux transport velocity remains comparable to the accretion velocity, so weaker field generation and slower transport combine to strongly suppress black-hole flux accumulation at smaller $h/r$. Correspondingly, the thinnest disk ($h/r=0.1$) produces an electromagnetic jet efficiency of only $η_{\\rm{EM}}\\sim1\\%$, while the thickest disk reaches the magnetically arrested disk (MAD) state and attains $η_{\\rm{EM}}\\geq100\\%$. Using the measured large-scale magnetic flux distribution and transport velocities, we estimate the time required to accumulate MAD-level magnetic flux. Only the $h/r\\sim0.3$ disk reaches MAD in the duration of our simulations, at $t\\simeq2\\times10^4\\,r_g/c$, whereas for $h/r=0.1$ we estimate a timescale of $\\sim10^8\\,r_g/c$. These results link disk geometry to magnetic-flux accumulation and jet launching, with direct implications for the timescales over which jets can emerge in transient accreting systems.",
  "abstract_shown": true,
  "affiliations": [],
  "article_type": null,
  "arxiv": "2610.37758",
  "author_total": 5,
  "authors": [
    {
      "name": "Jonatan Jacquemin-Ide"
    },
    {
      "name": "Mitchell C. Begelman"
    },
    {
      "name": "Henrik Latter"
    },
    {
      "name": "Jason Dexter"
    },
    {
      "name": "Alexander Tchekhovskoy"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/06287h9keydtm.bib",
  "cited_by": 0,
  "doi": "10.48550/arxiv.2610.37758",
  "fulltext_url": null,
  "id": "06287h9keydtm",
  "issns": [],
  "landing_url": "https://arxiv.org/abs/2610.37758",
  "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"
    ]
  ],
  "openalex": null,
  "pdf_url": "https://arxiv.org/pdf/2610.37758",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-27",
  "publisher": null,
  "ris": "https://research.draconitic.com/paper/06287h9keydtm.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:36:23Z",
      "native_id": "2610.37758",
      "source": "arxiv",
      "url": "https://arxiv.org/abs/2610.37758"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "arxiv:astro-ph.HE",
      "subfield": "high-energy-astrophysics"
    }
  ],
  "title": "Thinner Disks Struggle to Launch Jets: GRMHD Simulations of Magnetic Field Generation and Transport",
  "title_text": "Thinner Disks Struggle to Launch Jets: GRMHD Simulations of Magnetic Field Generation and Transport",
  "type": "preprint",
  "updated_at": "2026-11-01T12:20:44Z",
  "url": "https://research.draconitic.com/paper/06287h9keydtm",
  "venue": "arXiv",
  "versions": []
}