Journal article
Link between premidnight second harmonic poloidal waves and auroral undulations: Conjugate observations with a Van Allen Probe spacecraft and a THEMIS all‐sky imager
Journal of geophysical research. Space physics, Vol.120(3), pp.1814-1831
03/2015
DOI: 10.1002/2014JA020863
Abstract
We report, for the first time, an auroral undulation event on 1 May 2013 observed by the Time History of Events and Macroscale Interactions During Substorms (THEMIS) all‐sky imager (ASI) at Athabasca (L = 4.6), Canada, for which in situ field and particle measurements in the conjugate magnetosphere were available from a Van Allen Probe spacecraft. The ASI observed a train of auroral undulation structures emerging spontaneously in the premidnight subauroral ionosphere during the growth phase of a substorm. The undulations had an azimuthal wavelength of ~180 km and propagated westward at a speed of 3–4 km s−1. The successive passage over an observing point yielded quasiperiodic oscillations in diffuse auroral emissions with a period of ~40 s. The azimuthal wave number m of the auroral luminosity oscillations was found to be m~−103. During the event, the spacecraft—being on tailward stretched field lines ~0.5 RE outside the plasmapause that mapped into the ionosphere conjugate to the auroral undulations—encountered intense poloidal ULF oscillations in the magnetic and electric fields. We identify the field oscillations to be the second harmonic mode along the magnetic field line through comparisons of the observed wave properties with theoretical predictions. The field oscillations were accompanied by oscillations in proton and electron fluxes. Most interestingly, both field and particle oscillations at the spacecraft had one‐to‐one association with the auroral luminosity oscillations around its footprint. Our findings strongly suggest that this auroral undulation event is closely linked to the generation of second harmonic poloidal waves.
Key points
We report conjugate space‐ground observations for an undulation event
The auroral undulations concur with second harmonic poloidal waves
A common periodic signature is found in the conjugate aurora and magnetosphere
Details
- Title: Subtitle
- Link between premidnight second harmonic poloidal waves and auroral undulations: Conjugate observations with a Van Allen Probe spacecraft and a THEMIS all‐sky imager
- Creators
- T Motoba - Johns Hopkins University Applied Physics LaboratoryK Takahashi - Johns Hopkins University Applied Physics LaboratoryA Ukhorskiy - Johns Hopkins University Applied Physics LaboratoryM Gkioulidou - Johns Hopkins University Applied Physics LaboratoryD. G Mitchell - Johns Hopkins University Applied Physics LaboratoryL. J Lanzerotti - New Jersey Institute of TechnologyG. I Korotova - University of Maryland, College ParkE. F Donovan - University of CalgaryJ. R Wygant - University of MinnesotaC. A Kletzing - University of IowaW. S Kurth - University of IowaJ. B Blake - The Aerospace Corporation
- Resource Type
- Journal article
- Publication Details
- Journal of geophysical research. Space physics, Vol.120(3), pp.1814-1831
- DOI
- 10.1002/2014JA020863
- ISSN
- 2169-9380
- eISSN
- 2169-9402
- Number of pages
- 18
- Grant note
- NASA (NNX14AB97G; NNX12AK09G) NSF (AGS‐1207445) Canadian Space Agency
- Language
- English
- Date published
- 03/2015
- Academic Unit
- Physics and Astronomy
- Record Identifier
- 9984199947502771
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