Substorms Observed by Balloon­borne Instruments, Geostationary Particle Detectors, and the VIKING UV Imager: Pulsating Aurora
T. Freeman, M. McCarthy, G. Parks, and S. Werden (Geophysics Program, AK­50, University of Washington, Seattle, WA 98195)

R. Elphinstone and J. S. Murphree (University of Calgary, Calgary, Alberta, Canada)

J. Ducarteron and J. P. Treilhou (C. E. S. R., Toulouse, France)

Precipitation that accompanied the northward expansion of a substorm that occurred on July 26, 1986 included 5­15 second pulsations. This pulsation event was observed by a balloon­borne X­ray camera, magnetometer, and the VIKING UV imager. Both the UV and X­ray imager showed eastward drifting patches, which are characteristic of pulsating auroras. The UV patches had dimensions of ~40 x 200 km, and their apparent drift speed was a few hundred meters/s. The X­ray camera further showed that precipitation with dimensions ~15­20 km also occurred. This dimension is similar to the projected dimensions of the plasma sheet boundary layers in the ionosphere. The X­ray pulsations are associated with the softer component of a two component precipitation energy spectrum. This pulsating aurora included patches that appeared and disappeared on time scales of minutes, within which faster pulsations (10­15 seconds) occurred. A movie of this X­ray event will be shown.

23:36 UT
X­ray flux

[X-ray image]

movie: 23:20 - 23:55 UT

(animated GIF file, 276 k)

| Large­scale features | Relativistic dayside electron precipitation | Auroral X­ray imaging |