Density measurements in key regions of the Earth's magnetosphere: Cusp and auroral region

Journal Article · Tue May 01 04:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JA095iA05p05997· OSTI ID:5028893

Perraut, S; de Feraudy, H; Roux, A ^[1]; Decreau, P M.E. ^[2]; Paris, J ^[3]; Matson, L ^[4]

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1. Centre de Recherches en Physique de l'Environnement, Issy-les-Moulineaux (France)
2. Centre National de la Recherche Scientifique, Orleans (France)
3. Centre de Recherches en Physique de l'Environnement, Saint-Maur-des-Fosses (France)
4. Univ. of Umea (Sweden)

Two active experiments, a relaxation sounder and a mutual impedance probe, have been implemented on board Viking to determine the plasma density in the cusp region as well as in the sources of the auroral kilometric radiation (AKR). When active experiments are switched on in the cusp region, several plasma resonances are detected; they correspond to zero group velocity waves, indicative of a characteristic frequency of the plasma. Plasma density in the cusp proper is found to be much larger (> 100 cm{sup {minus}3} in some cases) than in the adjacent regions. An attempt is also made to estimate the respective densities and temperatures of the various components of the plasma. In contrast, auroral regions are low-density regions. The active sounding of the plasma by a relaxation sounder gives a resonance at f{sub uh}, which allows an estimate of the plasma density. Low-frequency whistler mode emissions are commonly observed in the night sector. Their upper cutoff frequency has often been used for estimating the plasma frequency. Active experiments are used to test this method, which is shown to be valid most of the time in the high-altitude auroral region, yet also sometimes misleading in other regions. Once the estimate of the density through the upper cutoff frequency of the hiss is validated, it can be used to follow with a good time resolution the sharp density variations experienced as Viking crossed AKR sources.

• OSTI ID: 5028893
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:A5; 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
AURORAL ZONES
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELECTROMAGNETIC RADIATION
LANGMUIR FREQUENCY
NOISE
PLASMA DENSITY
POLAR CUSP
RADIATIONS
RADIO NOISE
RADIOWAVE RADIATION
RESONANCE
TEMPERATURE MEASUREMENT
VARIATIONS
WHISTLERS