{
  "abstract": "We uncover a new pattern in the formation of fast coronal mass ejections (CMEs), consisting of three phases: a rapid lateral expansion ( hyperinflation ) lasting <10 minutes, followed by a slower but still asymmetric expansion, which lasts up to 50 minutes (both phases comprising the overexpansion ) and ending in the familiar self-similar expansion phase. The result is based on the analysis of 20 CMEs associated with flares and solar energetic particles (SEPs), which were comprehensively observed from multiple viewpoints at high cadence. To understand the role of the early expansion phase of CMEs in the formation of coronal shocks and consequent SEP acceleration, we studied the temporal relationship with other solar phenomena, including X-ray flares and radio emission. We find that (1) all events exhibit the three-stage formation sequence; (2) the overexpansion phase drives the shock and extreme-UV (EUV) wave, and explains why metric type II sources tend to form at CME flanks; (3) the hyperinflation phase is cotemporal to the flare impulsive phase, suggesting a common origin that is likely the addition of poloidal flux in the forming magnetic flux rope (MFR). Finally, we find that near-relativistic ∼53–105 keV) electrons are released first, near the flare peak and the onset of Type II. Note that ∼25 MeV protons are released later, toward the end of CME overexpansion, when shocks have formed. Our results clarify long-standing questions in the field and will contribute toward improved particle radiation forecasting schemes.",
  "abstract_shown": true,
  "affiliations": [
    "NASA Goddard Space Flight Center",
    "George Mason University",
    "The Johns Hopkins University Applied Physics Laboratory",
    "European Space Agency (ESA)",
    "Universidad de Alcalá",
    "University of Turku"
  ],
  "article_type": null,
  "arxiv": null,
  "author_total": 5,
  "authors": [
    {
      "affs": [
        0,
        1
      ],
      "name": "Laura A. Balmaceda",
      "orcid": "0000-0003-1162-5498"
    },
    {
      "affs": [
        2
      ],
      "name": "Angelos Vourlidas",
      "orcid": "0000-0002-8164-5948"
    },
    {
      "affs": [
        3,
        4
      ],
      "name": "Laura Rodríguez-García",
      "orcid": "0000-0003-2361-5510"
    },
    {
      "affs": [
        5
      ],
      "name": "Christian Palmroos"
    },
    {
      "affs": [
        5
      ],
      "name": "Nina Dresing",
      "orcid": "0000-0003-3903-4649"
    }
  ],
  "bibtex": "https://research.draconitic.com/paper/60qgghhqafs4g.bib",
  "cited_by": 0,
  "doi": "10.3847/1538-4357/aea083",
  "fulltext_url": null,
  "id": "60qgghhqafs4g",
  "issns": [
    "0004-637X",
    "1538-4357"
  ],
  "landing_url": "https://iopscience.iop.org/article/10.3847/1538-4357/aea083",
  "language": null,
  "licence": "CC-BY-4.0",
  "licence_label": "CC BY 4.0",
  "licence_source": "article",
  "licence_url": "https://creativecommons.org/licenses/by/4.0/",
  "metadata_licence": null,
  "native_subjects": [],
  "openalex": null,
  "pdf_url": "https://iopscience.iop.org/article/10.3847/1538-4357/aea083/pdf",
  "pmcid": null,
  "pmid": null,
  "published": "2026-10-09",
  "publisher": "American Astronomical Society",
  "ris": "https://research.draconitic.com/paper/60qgghhqafs4g.ris",
  "sources": [
    {
      "first_seen": "2026-10-30T12:18:11Z",
      "native_id": "10.3847/1538-4357/aea083",
      "source": "crossref",
      "url": "https://iopscience.iop.org/article/10.3847/1538-4357/aea083"
    }
  ],
  "subjects": [
    {
      "field": "astronomy",
      "origin": "journal-openalex:3103|Stellar, planetary, and galactic studies",
      "subfield": "stellar"
    }
  ],
  "title": "A New Understanding of the Formation Phases of Fast Coronal Mass Ejections and Their Role in Shock Formation and Particle Acceleration",
  "title_text": "A New Understanding of the Formation Phases of Fast Coronal Mass Ejections and Their Role in Shock Formation and Particle Acceleration",
  "type": "peer-reviewed",
  "updated_at": "2026-10-30T12:18:11Z",
  "url": "https://research.draconitic.com/paper/60qgghhqafs4g",
  "venue": "The Astrophysical Journal",
  "versions": []
}