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Titolo:
CUTLASS HF radar observations of high-velocity E-region echoes
Autore:
Uspensky, MV; Koustov, AV; Eglitis, P; Huuskonen, A; Milans, SE; Pulkkinen, T; Pirjola, R;
Indirizzi:
Finnish Meteorol Inst, Observ Serv, FIN-00101 Helsinki, Finland Finnish Meteorol Inst Helsinki Finland FIN-00101 00101 Helsinki, Finland Univ Saskatchewan, Dept Phys & Engn Phys, Saskatoon, SK S7N SE2, Canada Univ Saskatchewan Saskatoon SK Canada S7N SE2 skatoon, SK S7N SE2, Canada Swedish Inst Space Phys, S-75121 Uppsala, Sweden Swedish Inst Space Phys Uppsala Sweden S-75121 , S-75121 Uppsala, Sweden Univ Leicester, Dept Phys & Astron, Leicester LE1 7RH, Leics, England UnivLeicester Leicester Leics England LE1 7RH er LE1 7RH, Leics, England
Titolo Testata:
ANNALES GEOPHYSICAE
fascicolo: 4, volume: 19, anno: 2001,
pagine: 411 - 424
SICI:
0992-7689(200104)19:4<411:CHROOH>2.0.ZU;2-I
Fonte:
ISI
Lingua:
ENG
Soggetto:
AURORAL E-REGION; ELECTRON-DRIFT VELOCITY; LATITUDE E-REGION; IONOSPHERIC IRREGULARITIES; PLASMA IRREGULARITIES; ANGLE DEPENDENCE; COHERENT ECHOES; BACKSCATTER; DENSITY; REFRACTION;
Keywords:
ionosphere (ionospheric irregularities, plasma waves and instabilities, polar ionosphere);
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
42
Recensione:
Indirizzi per estratti:
Indirizzo: Uspensky, MV Finnish Meteorol Inst, Observ Serv, POB 503, FIN-00101 Helsinki, Finland Finnish Meteorol Inst POB 503 Helsinki Finland FIN-00101 and
Citazione:
M.V. Uspensky et al., "CUTLASS HF radar observations of high-velocity E-region echoes", ANN GEOPHYS, 19(4), 2001, pp. 411-424

Abstract

A short event of high-velocity E-region echo observations by the Pykkvibaer HF radar is analysed to study echo parameters and the echo relation to the Farley-Buneman plasma instability. The echoes were detected in several beams aligned closely to the magnetic L-shell direction. Two echo groups wereidentified: one group corresponded to the classical type 1 echoes with velocities close to the nominal ion-acoustic speed of 400 ms(-1), while the other group had significantly larger velocities, of the order of 700 ms(-1). The mutual relationship between the echo power, Doppler velocity, spectral width and elevation angles for these two groups was studied. Plotting of echo parameters versus slant range showed that all similar to 700 ms(-1) echoes originated from larger heights and distances of 500-700 km, while all similar to 400 ms(-1) echoes came from lower heights and from farther distances; 700-1000 km. We argue that both observed groups of echoes occurred due to the Farley-Buneman plasma instability excited by strong (similar to 70 mVm(-1)) and uniformly distributed electric fields. We show that the echo velocities for the two groups were different because the echoes were receivedfrom different heights. Such a separation of echo heights occult-ed due tothe differing amounts of ionospheric refraction at short and large ranges. Thus, the ionospheric refraction and related altitude modulation of ionospheric parameters are the most important factors to consider, when various characteristics of E-region decametre irregularities are derived from HF radar measurements.

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Documento generato il 25/11/20 alle ore 18:45:30