Rapid ray motions in barium plasma clouds and auroras
- Univ. of Alaska, Fairbanks (United States)
Barium plasma clouds released at high latitudes characteristically become striated with many field-aligned rays. The rays which often resemble auroral features usually drift as a whole with the E [times] B/B[sup 2] drift of the cloud and alter position only slowly (order or tens of seconds). On two evenings in 1968, in releases from Andoya, Norway, anomalous field-aligned brightenings or emission enhancements of up to 3X were observed to move rapidly (10-20 km/s) through three different Ba[sup +] clouds. Similar effects were observed in Ba[sup +] clouds released from rockets launched from Poker Flat, Alaska: On March 21, 1973, in two Ba thermite releases and on March 22, 1980, in the Ba-shaped charge experiment Miss Peggy.' On these occasions, auroras on or near the Ba[sup +] L shell, also exhibited active rapid ray motions. This leads to the assumption that the two phenomena are related and the expectation that an explanation of the rapid ray motions in the Ba[sup +] clouds would lead to a better understanding of the physics of auroral ray motions and the auroral ionosphere. Seven possible mechanisms to produce the observed moving emission enhancements are discussed. Direct motion of an isolated Ba[sup +] ray past the other rays by E [times] B/B[sup 2] motion seems very unlikely due to the observed variations in the enhancements and the large E field required (> 500 mV/m). Compressional waves do not seem to be of sufficient amplitude or velocity. Absorption or radiation of Doppler shifted Ba[sup +] emissions by ions gyrating or moving at a few kilometers per second seems to be the most promising mechanism for producing the enhancements. The observations provide compelling evidence for the existence of transient electric fields of order 100 mV/m at altitudes as low as 200 km during active aurora with rapid ray motions. The affected regions have dimensions of order a few kilometers across B and move eastward at 10-20 km/s. 36 refs., 10 figs., 1 tab.
- OSTI ID:
- 6873560
- Journal Information:
- Journal of Geophysical Research; (United States), Vol. 98:A3; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
AURORAE
PLASMA DRIFT
STRIATIONS
BARIUM IONS
EMISSION
IONOSPHERE
ABSORPTION
BARIUM
CLOUDS
CROSS SECTIONS
ELECTRIC FIELDS
ELECTRON DENSITY
ENERGY
EXCITATION
INSTABILITY
IONS
MOTION
PLASMA
VARIATIONS
VELOCITY
ALKALINE EARTH METALS
CHARGED PARTICLES
EARTH ATMOSPHERE
ELEMENTS
ENERGY-LEVEL TRANSITIONS
METALS
PLANETARY IONOSPHERES
SORPTION
661320* - Auroral
Ionospheric
& Magnetospheric Phenomena- (1992-)