Very large phase velocities of non two-stream, meter scale irregularities in the high latitude E region ionosphere
- Max-Planck Institute fuer Aeronomie, Katlenburg-Lindau (West Germany)
The authors present experimental evidence on a new category of meter wavelength radio auroral irregularities characterized by a unique Doppler spectrum signature. The new echoes were seen only be the Finland radar which observes at large angles to the electrojet flow and at times when the Norway radar observed very stable type 1 echoes with phase velocities near the ion acoustic speed. The new spectrum, named type 5, is composed of three main frequency bands, two being symmetric about zero Doppler shift near {plus minus}450 m/s and a third always at very large phase velocities near 1000 m/s, this resulting to a characteristic asymmetry in the spectrum. These echoes, which are not strong and last from a few minutes to tens of minutes, were observed during strong but also moderate geomagnetic conditions but, apparently, always in the presence of large and stable electric fields. The evidence suggested that the new echoes cannot be due to direct generation by the two-stream instability and, most likely, a secondary generation mechanism is involved. Although there are some similarities with 50 MHz type 4 spectral observations, type 5 echoes have unique characteristics which the authors believe are sufficient to justify their classification into a different echo category. They have no satisfactory theoretical explanation for the new echoes. That the fast moving irregularities have frequencies about two times the frequency of the simultaneously observed ion acoustic waves led them to suggest that a nonlinear resonant wave-wave interaction process might be in operation under some appropriate conditions in the plasma.
- OSTI ID:
- 5831640
- Journal Information:
- Journal of Geophysical Research; (USA), Vol. 94:A10; ISSN 0148-0227
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
GENERAL PHYSICS
E REGION
PLASMA INSTABILITY
AURORAE
ELECTRIC FIELDS
ELECTROJETS
ELECTRON DENSITY
GEOMAGNETIC FIELD
INTERACTIONS
ION WAVES
IONOSPHERE
NONLINEAR PROBLEMS
RADAR
RADIOWAVE RADIATION
TWO-STREAM INSTABILITY
CURRENTS
EARTH ATMOSPHERE
ELECTRIC CURRENTS
ELECTROMAGNETIC RADIATION
INSTABILITY
MAGNETIC FIELDS
MEASURING INSTRUMENTS
PLANETARY IONOSPHERES
PLASMA MICROINSTABILITIES
PLASMA WAVES
RADIATIONS
RANGE FINDERS
640201* - Atmospheric Physics- Auroral
Ionospheric
& Magetospheric Phenomena