Energetics and Alfvénic Coupling of a Poleward Boundary Intensification: A Polar Case Study

Andreas Keiling, John Wygant, Matthew Fillingim, Karlheinz J. Trattner

Research output: Contribution to journalArticlepeer-review


The poleward boundary intensification (PBI) is a common appearance at the poleward boundary of the auroral bulge and auroral oval. The PBI presented here occurred during the expansion phase of a small substorm with an auroral surge power of 6.5 GW. The auroral power of the PBI (1.1 GW) was ~17% of this value. The largest powers above the nominal auroral acceleration region at 5 RE geocentric were carried by Alfvén waves (1.7 GW) and Alfvénic electrons (0.7 GW), sufficient to account for the conjugate PBI auroral power. In contrast, the conjugate quasistatic, field-aligned current power (<0.3 GW) was not sufficient. Observed correlation between quasiperiodic Alfvénic pulses and auroral modulations strengthens our conclusion that the electromagnetic magnetosphere-ionosphere coupling of the PBI was dominantly Alfvénic, as opposed to electrostatic, thus causing Alfvénic aurora.

Original languageEnglish (US)
Article numbere2020JA028041
JournalJournal of Geophysical Research: Space Physics
Issue number8
StatePublished - Aug 1 2020

Bibliographical note

Funding Information:
This research was supported by the NSF Grant AGS‐1613134.

Publisher Copyright:
©2020. American Geophysical Union. All Rights Reserved.


  • Alfvén wave
  • ULF wave
  • aurora
  • energy transfer
  • magnetosphere-ionosphere coupling
  • substorm


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