Equatorial density depletions observed at 840 km during the great magnetic storm of March 1989

Journal Article · Thu Aug 01 04:00:00 EDT 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/91JA01264· OSTI ID:5008792

Greenspan, M E ^[1]; Rasmussen, C E ^[2]; Burke, W J ^[3]; Abdu, M A ^[4]

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1. Boston Univ., MA (United States)
2. Univ. of Michigan, Ann Arbor (United States)
3. Phillips Lab., Hanscom Air Force Base, MA (United States)
4. Inst. Nacional de Pesquisas Espaciais, Sao Paulo (Brazil)

Early on March 14, 1989, a thermal plasma probe on the Defense Meteorological Satellite Program (DMSP) F9 spacecraft detected extensive and dramatic decreases in the ion density at 840 km, near 2130 LT, during two consecutive transequatorial passes over South America. The order of magnitude decreases in the ion density extended more than 4,000 km along the satellite track. The depletions were accompanied by upward and westward plasma drifts, both in excess of 100 m/s. Their onsets and terminations were marked by extremely sharp density gradients. A partial depletion was detected over the eastern Pacific during the following orbit. The DMSP F9 ground track passed slightly west of a Brazilian total electron content (TEC) station and two Brazilian ionosondes during the first depletion encounter. The TEC fell far below normal during the night of March 13-14. The ionosonde measurements indicate that, in the hour after sunset, before DMSP passed through the depletions, the F{sub 2} layer rose rapidly and disappeared, but at the time of the first depletion encounter, h{sub m}F{sub 2} was decreasing over one of the stations. The authors develop a phenomenological model reconciling DMSP F8, F9 and ground-based measurements. The calculations show that rapid upward drifts sustained for several hours can produce depletions in the equatorial ion density with sharp gradients at their high-latitude boundaries, consistent with the data. They discuss possible contributing mechanisms for generating these upward drifts. These include direct penetration of the magnetospheric electric field to low latitudes, the electric fields generated by the disturbance dynamo, and the effects of conductivity gradients near the dusk terminator and the South Atlantic anomaly.

• OSTI ID: 5008792
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 96:A8; 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
ALTITUDE
EARTH ATMOSPHERE
ELECTRIC FIELDS
ELECTRON DENSITY
ELECTRONIC EQUIPMENT
EQUIPMENT
F REGION
F2 LAYER
ION DENSITY
IONOSONDES
IONOSPHERE
IONOSPHERIC EFFECTS
LATIN AMERICA
MAGNETIC STORMS
MATHEMATICAL MODELS
PLANETARY IONOSPHERES
PLASMA DENSITY
PLASMA DRIFT
RADIO EQUIPMENT
SATELLITES
SOUTH AMERICA