Magnetic signatures of precursors to substorm expansive phase onset

Journal Article · Mon Jun 01 04:00:00 EDT 1987 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA092iA06p05845· OSTI ID:5876000

de Groot-Hedlin, C D; Rostoker, G ^[1]

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1. Univ. of Alberta, Edmonton (Canada)

The expansive phase of magnetospheric substorms involves the development of auroral loops and surges with particular emphasis on the westward travelling surge which is identified with the western edge of the substorm current wedge. The authors use as a working hypothesis the contention that the wavelike auroral structures associated with the current wedge are a manifestation of the action of a Kelvin-Helmholtz instability at the interface between the central plasma sheet (CPS) and the adjacent boundary layer plasmas in the deep magnetotail. Based on this concept, they used ground-based magnetometer data in an attempt to identify the growth of ionospheric current systems which might be associated with the growth of the Kelvin-Helmholtz instability. They have, in fact, found that the expansive phase is preceded by the growth of a weak substorm current wedge which strengthens explosively at the time of onset. They suggest that field-aligned current flows out of the ionosphere as part of a process damping a growing wave at the CPS/boundary layer interface. When the field-aligned current density exceeds {approximately} 1 {mu}A/m{sup 2}, an acceleration region at altitudes of {approximately} 1 R{sub E} is activated marking the onset of the substorm expansive phase.

• OSTI ID: 5876000
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 92:A6; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

661320* -- Auroral
Ionospheric
& Magnetospheric Phenomena-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCELERATION
AURORAE
AURORAL OVAL
CURRENT DENSITY
CURRENTS
DAMPING
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELECTRIC CURRENTS
ELECTRODYNAMICS
ELECTROJETS
ENERGY STORAGE
ENERGY TRANSFER
EXPANSION
HELMHOLTZ INSTABILITY
INSTABILITY
IONOSPHERE
MAGNETIC BAYS
MAGNETOTAIL
PLANETARY IONOSPHERES
PLASMA INSTABILITY
PLASMA MACROINSTABILITIES
PLASMA SHEET
SOLAR ACTIVITY
SOLAR WIND
STORAGE