The ionospheric signatures of flux transfer events and solar wind dynamic pressure changes

Journal Article · Mon Oct 01 00:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA095iA10p17113· OSTI ID:5102867

Lockwood, M ^[1]; Cowley, S W.H. ^[2]; Sandholt, P E ^[3]; Lepping, R P ^[4]

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1. Rutherford Appleton Lab., Chilton (England) Imperial College, London (England)
2. Imperial College, London (England)
3. Univ. of Oslo (Norway)
4. Goddard Space Flight Center, Greenbelt, MD (United States)

The generation of flow and current vortices in the dayside auroral ionosphere has been predicted for two processes occurring at the dayside magnetopause. The first of these mechanisms is time-dependent magnetic reconnection, in flux transfer events (FTEs); the second is the action of solar wind dynamic pressure changes. The ionospheric flow signature of an FTE should be a twin vortex, with the mean flow velocity in the central regon of the pattern equal ot the velocity of the pattern as a whole. On the other hand, a pulse of enhanced or reduced dynamic pressure is also expected to produce a twin vortex, but with the central plasma flow being generally different in speed from, and almost orthogonal to, the motion of the whole pattern. In this paper, the authors make use of this distinction to discuss recent observations of vortical flow patterns in the dayside auroral ionosphere in terms of one or other of the proposed mechanisms. They conclude that some of the observatons reported are consistent only with the predicted signature of FTEs. They then evaluate the dimensions of the open flux tubes required to explain some recent simultaneous radar and auroral observatons and infer that they are typically 300 km in north-south extent but up to 2,000 km in longitudinal extent (i.e., roughly 5 hours of MLT). Hence these observations suggest that recent theories of FTEs which invoke time-varying reconnecton at an elongated neutral line may be correct.

• OSTI ID: 5102867
• Journal Information: Journal of Geophysical Research; (United States), Vol. 95:A10; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAL ZONES
ELECTRIC CURRENTS
PLASMA DRIFT
MAGNETOPAUSE
MAGNETIC RECONNECTION
PLASMA PRESSURE
INTERACTIONS
INTERPLANETARY MAGNETIC FIELDS
IONOSPHERIC EFFECTS
MAGNETIC FLUX
SOLAR WIND
TIME DEPENDENCE
VARIATIONS
VORTICES
CURRENTS
MAGNETIC FIELDS
SOLAR ACTIVITY
640201* - Atmospheric Physics- Auroral
Ionospheric
& Magetospheric Phenomena