Substorm-associated radar auroral surges

Journal Article · Sat Aug 01 00:00:00 EDT 1992 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/92JA00697· OSTI ID:7172953

Freeman, M P; Southwood, D J ^[1]; Lester, M; Yeoman, T K ^[2]; Reeves, G D ^[3]

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1. Imperial Coll., London (United Kingdom)
2. Leicester Univ. (United Kingdom)
3. Los Alamos National Lab., NM (United States)

The authors report a recurrent convection signature observed in the E region ionosphere within {approximately}2 hours of the dusk meridian by the SABRE radar facility. In a typical event, the irregularity drift speed in the SABRE field of view is seen to increase from about 300 m s{sup {minus}1} to of the order of 1 km s{sup {minus}1} in the space of about 10 min. The speed subsequently remains at the enhanced level for 10 min or longer before declining as rapidly as its onset. The total event duration ranges between 30 min and 1 hour. As the irregularity drift speed increases the direction of the drift velocity changes, rotating poleward. At the same time, the radar backscatter power decreases. The onset of the drift speed enhancement crosses the SABRE field of view as a front moving from east to west. Detailed study of individual events indicates that the events are associated with increases in the {vert bar}AL{vert bar} index and with the injection of energetic particles into geosynchronous orbit. The authors thus suggest that the events are a part of the magnetospheric response to the onset of a geomagnetic substorm. However, while each event appears to be associated with a substorm onset, not every substorm onset is associated with an event, at least not at SABRE. They estimate the speed at which the substorm-initiated ionospheric flow enhancement moves from the nightside to be 1-4 km s{sup {minus}1}, a figure that is consistent with the rate at which the drift velocity front crosses the SABRE field of view. Although the front is associated with a rotation in the drift velocity, they see little evidence of strong vertical vorticity as the front passes. However, shears in the flow do develop subsequently which seem likely to correspond to field-aligned current. Although associated with substorm onset, they argue that these events are distinct from westward traveling surges and appear to differ from the midlatitude phenomenon known as subauroral ion drifts.

• OSTI ID: 7172953
• Journal Information: Journal of Geophysical Research; (United States), Vol. 97:A8; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAE
MAGNETIC BAYS
E REGION
EARTH MAGNETOSPHERE
ELECTRIC CURRENTS
ELECTROJETS
EXPANSION
ION DRIFT
PHASE VELOCITY
PLASMA DRIFT
RADAR
SHEAR
CURRENTS
EARTH ATMOSPHERE
IONOSPHERE
MEASURING INSTRUMENTS
PLANETARY IONOSPHERES
RANGE FINDERS
VELOCITY
661320* - Auroral
Ionospheric
& Magnetospheric Phenomena- (1992-)