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Energetics and Alfvénic Coupling of a Poleward Boundary Intensification: A Polar Case Study
Author(s) -
Keiling Andreas,
Wygant John,
Fillingim Matthew,
Trattner Karlheinz J.
Publication year - 2020
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1029/2020ja028041
Subject(s) - substorm , physics , magnetosphere , ionosphere , geophysics , alfvén wave , polar , coupling (piping) , computational physics , electron , quantum electrodynamics , astrophysics , magnetic field , magnetohydrodynamics , astronomy , nuclear physics , quantum mechanics , mechanical engineering , engineering
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 R E 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.