Physics
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009georl..3623106s&link_type=abstract
Geophysical Research Letters, Volume 36, Issue 23, CiteID L23106
Physics
5
Magnetospheric Physics: Auroral Phenomena (2407), Magnetospheric Physics: Mhd Waves And Instabilities (2149, 6050, 7836), Magnetospheric Physics: Magnetosphere/Ionosphere Interactions (2431)
Scientific paper
The time evolution of optical structures in brightening auroras was examined for two substorm events that occurred on January 15, 2008 and February 27, 2009. The onsets of both auroral substorms were captured in the field of view of an all-sky TV camera at Gillam, Canada. We found that in both cases, the brightening auroras formed vertical structures, or so-called ‘ray auroras’, which lined up longitudinally for several tens of seconds before luminosity increased sharply. The ray structure implies precipitating electrons accelerated over a broad energy range at substorm onset. Two dimensional Fourier transform analysis of the auroral images showed the ray auroras have characteristic wavenumbers and harmonics that develop within a few seconds of the initial brightening. These results suggest that dispersive Alfvén waves containing turbulent parallel electric fields form in brightening regions at the beginning of auroral substorms.
Donovan Eric
Sakaguchi Kei
Shiokawa Kazuhiko
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