Viking observations at the source region of auroral kilometric radiation

Journal Article · Thu Jun 01 00:00:00 EDT 1989 · Journal of Geophysical Research; (USA)

DOI:https://doi.org/10.1029/JA094iA06p06643· OSTI ID:5831172

Bahnsen, A; Jespersen, M; Ungstrup, E ^[1]; Pedersen, B M ^[2]; Eliasson, L ^[3]; Murphree, J S; Elphinstone, R D ^[4]; Blomberg, L ^[5]; Holmgren, G ^[6]; Zanetti, L J ^[7]

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1. Danish Space Research Institute, Lyngby (Denmark)
2. Observatory of Paris, Meudon (France)
3. Swedish Institute of Space Physics, Kiruna (Sweden)
4. Univ. of Calgary, Alberta (Canada)
5. Royal Institute of Technology, Stockholm (Sweden)
6. Swedish Institute of Space Physics, Uppsala (Sweden)
7. Johns Hopkins Univ., Laurel, MD (USA)

The orbit of the Swedish satellite Viking was optimized for in situ observations of auroral particle acceleration and related phenomena. In a large number of the orbits, auroral kilometric radiation (AKR) was observed, and in approximately 35 orbits the satellite passed through AKR source regions as evidenced by very strong signals at the local electron cyclotron frequency f{sub ce}. These sources were found at the poleward edge of the auroral oval at altitudes, from 5,000 to 8,000 km, predominantly in the evening sector. The strong AKR signal has a sharp low-frequency cutoff at or very close to f{sub ce} in the source. In addition to AKR, strong broadband electrostatic noise is measured during the source crossings. Energetic (1-15 keV) electrons are always present at and around the AKR sources. Upward directed ion beams of several keV are closely correlated with the source as are strong and variable electric fields, indicating that a region of upward pointing electric field below the observation point is a necessary condition for AKR generation. The plasma density is measured by three independent experiments and it is generally found that the density is low across the whole auroral oval. For some source crossings the three methods agree and show a density depletion (but not always confined to the source region itself), but in many cases the three measurements do not yield consistent results. The magnetic projection of the satellite passes through auroral forms during the source crossings, and the strongest AKR events seem to be connected with kinks in an arc or more complicated structures.

• OSTI ID: 5831172
• Journal Information: Journal of Geophysical Research; (USA), Journal Name: Journal of Geophysical Research; (USA) Vol. 94:A6; 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
ACCELERATION
AURORAL OVAL
BEAMS
CHARGED PARTICLES
EARTH ATMOSPHERE
EARTH MAGNETOSPHERE
ELECTRIC FIELDS
ELECTROMAGNETIC RADIATION
ELECTRONS
ELEMENTARY PARTICLES
FERMIONS
ION BEAMS
IONOSPHERE
LEPTONS
LONG WAVE RADIATION
PLANETARY IONOSPHERES
PLASMA DENSITY
RADIATIONS
RADIOWAVE RADIATION
SATELLITES
WAVE PROPAGATION