Near-Earth injection of MeV electrons associated with intense dipolarization electric fields: Van Allen Probes observations.

Geophysical research letters · 2015 · Unclear · Insufficient evidence

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UnclearInsufficient evidencePaper 2923

Study snapshot

PublicationGeophysical research letters · 2015

Study typeother

Reported directionUnclear

Evidence ratingInsufficient

Abstract

Substorms generally inject tens to hundreds of keV electrons, but intense substorm electric fields have been shown to inject MeV electrons as well. An intriguing question is whether such MeVelectron injections can populate the outer radiation belt. Here we present observations of a substorm injection of MeV electrons into the inner magnetosphere. In the premidnight sector at ∼ 5.5, Van Allen Probes (Radiation Belt Storm Probes)-A observed a large dipolarization electric field (50 mV/m) over ∼40 s and a dispersionless injection of electrons up to ∼3 MeV. Pitch angle observations indicated betatron acceleration of MeV electrons at the dipolarization front. Corresponding signals of MeV electron injection were observed at LANL-GEO, THEMIS-D, and GOES at geosynchronous altitude. Through a series of dipolarizations, the injections increased the MeV electron phase space density by 1 order of magnitude in less than 3 h in the outer radiation belt ( > 4.8). Our observations provide evidence that deep injections can supply significant MeV electrons.

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AI evidence extraction

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Study typeother

Effect directionunclear

PopulationNot supplied

Sample sizeNot supplied

Exposure~40 s (dipolarization electric field observed)

Evidence strengthInsufficientConfidence: 74% · Peer reviewed: yes

Main findings

Van Allen Probes-A observed a large dipolarization electric field (~50 mV/m) lasting ~40 s and a dispersionless injection of electrons up to ~3 MeV. Across a series of dipolarizations, injections were associated with an increase in MeV electron phase space density by ~1 order of magnitude in less than 3 h in the outer radiation belt (>4.8), with pitch angle observations indicating betatron acceleration at the dipolarization front.

Outcomes measured

MeV electron injection into inner magnetosphere/outer radiation belt
Dipolarization electric field magnitude (50 mV/m)
Electron energies up to ~3 MeV
MeV electron phase space density change (order-of-magnitude increase in <3 h)
Pitch angle signatures consistent with betatron acceleration

View raw extracted JSON

{
  "study_type": "other",
  "exposure": {
    "band": null,
    "source": null,
    "frequency_mhz": null,
    "sar_wkg": null,
    "duration": "~40 s (dipolarization electric field observed)"
  },
  "population": null,
  "sample_size": null,
  "outcomes": [
    "MeV electron injection into inner magnetosphere/outer radiation belt",
    "Dipolarization electric field magnitude (50 mV/m)",
    "Electron energies up to ~3 MeV",
    "MeV electron phase space density change (order-of-magnitude increase in <3 h)",
    "Pitch angle signatures consistent with betatron acceleration"
  ],
  "main_findings": "Van Allen Probes-A observed a large dipolarization electric field (~50 mV/m) lasting ~40 s and a dispersionless injection of electrons up to ~3 MeV. Across a series of dipolarizations, injections were associated with an increase in MeV electron phase space density by ~1 order of magnitude in less than 3 h in the outer radiation belt (>4.8), with pitch angle observations indicating betatron acceleration at the dipolarization front.",
  "effect_direction": "unclear",
  "limitations": [],
  "evidence_strength": "insufficient",
  "confidence": 0.74,
  "peer_reviewed_likely": "yes",
  "keywords": [
    "substorm",
    "dipolarization electric field",
    "MeV electrons",
    "electron injection",
    "Van Allen Probes",
    "outer radiation belt",
    "betatron acceleration",
    "phase space density",
    "geosynchronous observations"
  ],
  "suggested_hubs": []
}

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AI-extracted fields are generated from the abstract and metadata and may be incomplete or incorrect. This material is for informational purposes and is not medical advice.

Identifiers and source

DOI: 10.1002/2015gl064955
PubMed: 27656009

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