Optical characterization of the growth and spatial structure of a substorm onset arc

DOI Web Site Web Site 被引用文献4件
  • I. J. Rae
    Department of Physics University of Alberta Edmonton, Alberta Canada
  • C. E. J. Watt
    Department of Physics University of Alberta Edmonton, Alberta Canada
  • I. R. Mann
    Department of Physics University of Alberta Edmonton, Alberta Canada
  • K. R. Murphy
    Department of Physics University of Alberta Edmonton, Alberta Canada
  • J. C. Samson
    Department of Physics University of Alberta Edmonton, Alberta Canada
  • K. Kabin
    Department of Physics University of Alberta Edmonton, Alberta Canada
  • V. Angelopoulos
    Institute of Geophysics and Planetary Physics University of California, Los Angeles (UCLA) Los Angeles California USA

書誌事項

公開日
2010-10
権利情報
  • http://onlinelibrary.wiley.com/termsAndConditions#vor
DOI
  • 10.1029/2010ja015376
公開者
American Geophysical Union (AGU)

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説明

<jats:p>We present a detailed case study of the characteristics of auroral forms that constitute the first ionospheric signatures of substorm expansion phase onset. Analysis of the optical frequency and along‐arc (azimuthal) wave number spectra provides the strongest constraint to date on the potential mechanisms and instabilities in the near‐Earth magnetosphere that accompany auroral onset and which precede poleward arc expansion and auroral breakup. We evaluate the frequency and growth rates of the auroral forms as a function of azimuthal wave number to determine whether these wave characteristics are consistent with current models of the substorm onset mechanism. We find that the frequency, spatial scales, and growth rates of the auroral forms are most consistent with the cross‐field current instability or a ballooning instability, most likely triggered close to the inner edge of the ion plasma sheet. This result is supportive of a near‐Earth plasma sheet initiation of the substorm expansion phase. We also present evidence that the frequency and phase characteristics of the auroral undulations may be generated via resonant processes operating along the geomagnetic field. Our observations provide the most powerful constraint to date on the ionospheric manifestation of the physical processes operating during the first few minutes around auroral substorm onset.</jats:p>

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