A rotating, midday auroral event with northward interplanetary magnetic field
Journal Article
·
· Journal of Geophysical Research
- Univ. of Oslo (Norway)
- Phillips Lab., Hanscom Air Force Base, MA (United States)
The authors present ground-based observations of an isolated, daytime auroral event that was detected above Svalbard by means of an all-sky TV camera and a multichannel, meridian scanning photometer. This 5-min event occurred near magnetic noon, poleward of a stable cusp aurora. It emitted {approximately} 20 kR of 557.7-nm light, with little if any admixture of 630.0-nm radiation. The structure rotated rapidly then underwent a sudden breakup. The spectral distribution of emitted light indicates that electrons responsible for this auroral structure were accelerated though several kilovolts between the magnetosheath and the ionosphere. Such a potential structure requires that the precipitating, arc electrons constitute a field-aligned current out of the ionosphere. Current continuity and Ohm`s law require radial electric fields within the arc. From the structure`s rotational speed, the authors estimate that the accelerated electrons carried an upward field-aligned current of order 100{mu}A/m{sup 2}. Satellite observations of polar cap convection patterns suggest that the interplanetary magnetic field had turned northward prior to the event. The auroral structure may be explained as resulting from a transitory magnetic merging of interplanetary and lobe magnetic field lines at and/or a penetration of plasma across the high-latitude magnetopause. 40 refs., 3 figs.
- OSTI ID:
- 96515
- Journal Information:
- Journal of Geophysical Research, Journal Name: Journal of Geophysical Research Journal Issue: A8 Vol. 98; ISSN JGREA2; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
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