Doppler radar observations of harmonics of electrostatic ion cyclotron waves in the auroral ionosphere

Journal Article · Fri Jul 01 00:00:00 EDT 1988 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA093iA07p07409· OSTI ID:6952765

Prikryl, P; Andre, D; Sofko, G J; Koehler, J A

Observations of short-lived scattering events (0.5 s to 1 min) have been made with cross-beamed 50-MHz CW Doppler radars. Doppler spectra with high resolution in both frequency and time are obtained by detailed processing of time series digitized at high analogue to digital conversion rates. The spectra are highly structured, showing bursts of power at groups of discrete frequencies that are very short lived (usually approx.50 ms). Discrete spectral peaks can be found at Doppler velocities as high as 2500 m/s. The frequency separation between the successive discrete components of a group is often approximately the cyclotron frequency of one of the principal ions in the E region (NO/sup +/, O/sup +//sub 2/, N/sup +//sub 2/, and O/sup +/), so the components are postulated to be harmonics of electrostatic ion cyclotron (EIC) waves at elevated beam electron temperatures (more than 1000 K) in the upper E region. These transient events are closely correlated with intense auroral arc brightenings and/or the onset of auroral breakup, when high temperatures, strong field-aligned particle drifts, and field-aligned currents can be anticipated. Numerical solutions of the kinetic dispersion relation for a range of ionospheric parameters, especially the parallel electron drift velocity and beam temperature, reveal that both the higher and lower harmonics of EIC waves can become unstable. Thus some of the rapid time variation of the observed spectral peaks in the transient events can be explained by an appropriate accompanying change in ionospheric parameters. copyright American Geophysical Union 1988

• Research Organization: Institute of Space and Atmospheric Studies, University of Saskatchewan Saskatoon, Canada
• OSTI ID: 6952765
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 93:A7; 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
AURORAE
CYCLOTRON FREQUENCY
DISPERSION RELATIONS
E REGION
EARTH ATMOSPHERE
ELECTRON DRIFT
HARMONICS
ION PLASMA WAVES
ION TEMPERATURE
ION WAVES
IONOSPHERE
MEASURING INSTRUMENTS
OSCILLATIONS
PLANETARY IONOSPHERES
PLASMA WAVES
RADAR
RANGE FINDERS