Low altitude signature of the plasma sheet boundary layer: Observations and model

Journal Article · Sat Apr 01 04:00:00 EST 1995 · Geophysical Research Letters

DOI:https://doi.org/10.1029/95GL00304· OSTI ID:166232

Onsager, T G ^[1]; Mukai, T ^[2]

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1. Univ. of New Hampshire, Durham, NH (United States)
2. Institute of Space and Astronautical Science, Sagamihara (Japan)

Low-altitude spacecraft on magnetotail field lines often detect a distinctive signature in the precipitating ion flux. A velocity-dispersed ion structure is often observed near the poleward boundary of the auroral oval. At the low-latitude edge of this structure an absence of precipitating ions is seen, previously referred to as {open_quotes}the gap,{close_quotes} separating the velocity-dispersed ions at the higher latitudes from the more diffuse, plasma sheet-like ions at lower latitudes. The authors present a model of low-altitude particle precipitation that reproduces these observed features in the ion spectra and provides a quantitative estimate of the downtail plasma sheet properties. The model calculations are compared with observations from the Akebono spacecraft. In this model, the dispersed ion velocity signature maps to a region in the distant plasma sheet where the plasma has a field-aligned bulk flow. The gap maps to a region in the distant magnetotail where the ion fluxes are below the detection threshold of the instrument, due to the low plasma sheet density and temperature in that region. 15 refs., 2 figs.

• OSTI ID: 166232
• Journal Information: Geophysical Research Letters, Journal Name: Geophysical Research Letters Journal Issue: 7 Vol. 22; ISSN GPRLAJ; ISSN 0094-8276
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
AURORAL OVAL
BOUNDARY LAYERS
CHARGED-PARTICLE PRECIPITATION
MAGNETIC FIELDS
MAGNETOTAIL
MAPPING
PLASMA SHEET