The altitude of type 3 auroral irregularities: Radar interferometer observations and implications

Journal Article · Tue Oct 01 00:00:00 EDT 1991 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/91JA01544· OSTI ID:5812915

Sahr, J D; Farley, D T; Swartz, W E ^[1]; Providakes, J F ^[2]

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1. Cornell Univ., Ithaca, NY (United States)
2. MITRE Corp., Bedford, MA (United States)

VHF coherent scatter radars at auroral latitudes have observed scatterers with narrow power spectra at sub-ion acoustic mean Doppler shifts. These spectra have been designated type 3. The mean Doppler shift of these waves is often near the atomic (O{sup +}) or, less frequently, the molecular (O{sub 2}{sup +} and NO{sup +}) gyro frequencies. These type 3 echoes have been attributed to an electrostatic ion-cyclotron (EIC) instability in the upper E region (h > 140 km), where the ion collision frequency becomes low enough to permit ion gyromotion. Interferometric analysis of recent coherent radar observations with the CUPRI (Cornell University portable radar interferometer) shows that type 3 events occur at typical electrojet altitudes (100-120 km), however. At these altitudes the ion collision frequency is greater than the ion gyrofrequency and there can be no cyclotron motion. The cause of the observed type 3 echoes hence remains a mystery.

• OSTI ID: 5812915
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 96:A10; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

661320* -- Auroral
Ionospheric
& Magnetospheric Phenomena-- (1992-)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
AURORAL ZONES
CHALCOGENIDES
CURRENTS
CYCLOTRON FREQUENCY
DOPPLER EFFECT
E REGION
EARTH ATMOSPHERE
ELECTRIC CURRENTS
ELECTROJETS
ELEMENTS
INSTABILITY
INTERFEROMETRY
ION WAVE INSTABILITY
ION WAVES
IONOSPHERE
LEVELS
MEASURING INSTRUMENTS
NITRIC OXIDE
NITROGEN COMPOUNDS
NITROGEN OXIDES
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PLANETARY IONOSPHERES
PLASMA INSTABILITY
PLASMA MICROINSTABILITIES
PLASMA WAVES
RADAR
RANGE FINDERS
SCATTERING
SPECTRA