CUTLASS HF radar observations of high-velocity E-region echoes

MV Uspensky*, AV Koustov, P Eglitis, A Huuskonen, SE Milans, T Pulkkinen, R Pirjola

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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 were identified: 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 received from different heights. Such a separation of echo heights occult-ed due to the 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.

Original languageEnglish
Pages (from-to)411-424
Number of pages14
JournalAnnales Geophysicae
Volume19
Issue number4
Publication statusPublished - Apr 2001
MoE publication typeA1 Journal article-refereed

Keywords

  • ionosphere (ionospheric irregularities, plasma waves and instabilities, polar ionosphere)
  • AURORAL E-REGION
  • ELECTRON-DRIFT VELOCITY
  • LATITUDE E-REGION
  • IONOSPHERIC IRREGULARITIES
  • PLASMA IRREGULARITIES
  • ANGLE DEPENDENCE
  • COHERENT ECHOES
  • BACKSCATTER
  • DENSITY
  • REFRACTION

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