Mapping and distortions of auroral structures in the quiet magnetosphere

Journal Article · Fri Jun 01 04:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA095iA06p07973· OSTI ID:5268476

Kaufmann, R L; Larson, D J; Lu, Chen ^[1]

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1. Univ. of New Hampshire, Durham (USA)

The objective of this report is to identify those features of commonly observed dayside auroras that can be explained easily by either of two processes: mapping distortions or distortions caused by nearby Birkeland currents. Mapping distortions in a quiet closed magnetosphere model yield very elongated arclike ionospheric images in the dayside auroral zone for a wide range of circular or elliptical tubelike equatorial sources. The length of a dayside auroral arc provides a good measure of the equatorial source dimension normal to the magnetopause. The orientation of the dayside arc provides a crude estimate of the solar magnetospheric x location of the equatorial source. Dayside arcs and Birkeland currents are found to map to both the dayside and the nightside magnetopause current layer and low latitude boundary layer. Nightside auroral arcs and Birkeland currents map to the magnetotail plasma sheet and plasma sheet boundary layer. Localized Birkeland currents produce characteristic distortions that are dependent on the current density gradient. Single and multiple linear and hooked auroral forms are easy to understand in terms of mapping distortions in a quiet magnetosphere. The shapes of bright twisted or folded auroral forms are more easily explained as distortions produced by localized Birkeland currents. Measurement of the size of a spiral auroral structure provides an estimate of the current magnitude. Relationships between the motion of ionospheric objects and the motion of equatorial sources are summarized by two color plates. Such motion sometimes differs markedly from what one might intuitively expect. For example, some tailward moving sources near the magnetopause can map to sunward moving ionospheric images.

• OSTI ID: 5268476
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:A6; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640201* -- Atmospheric Physics-- Auroral
Ionospheric
& Magetospheric Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAE
AURORAL ZONES
BOUNDARY LAYERS
CURRENTS
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELECTRIC CURRENTS
ELECTRIC FIELDS
LAYERS
MAGNETIC FLUX
MAGNETOPAUSE
MAGNETOTAIL
MAPPING
MATHEMATICAL MODELS
ORIENTATION
PLASMA SHEET
VORTICES