Excitation of short-scale field-aligned electron density irregularities by ionospheric topside sounders

Research output: Contribution to journalArticle

Abstract

Generation of short-scale field-aligned electron density irregularities on a short timescale (≪ 1 s) by ionospheric topside sounder pulses is studied. It is a four-wave parametric coupling process, in which a sounder-launched Z mode pump wave decays into two electron Bernstein sidebands and a geomagnetic field-aligned density irregularity. The dispersion relation of the parametric coupling process has been derived and analyzed. The results show that meter-scale field-aligned electron density irregularities (FAI) can be excited with growth rates of the order of 105 s-1 under the resonance conditions that fo≅fp≅ nfc, where fo, fp, and fc are the pump wave frequency, electron plasma frequency, and electron cyclotron frequency, respectively, and n is an integer. The excited FAI extend along the magnetic field toward the satellite path, causing the incoherent scattering of the subsequently transmitted sounding pulses. This is suggested to be a possible cause of long-duration Z mode echoes appearing on the Alouette 2 ionograms when fo ≅ fp≅ nfc, as reported by Benson [1997]. It is found that the threshold field of the instability decreases with increased n. It may explain why long-duration Z mode echoes were only observed when n ≥ 4.

Original languageEnglish (US)
Article number1999JA900232
Pages (from-to)19889-19894
Number of pages6
JournalJournal of Geophysical Research: Space Physics
Volume104
Issue numberA9
StatePublished - 1999

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sounding
irregularities
electron density
ionospherics
Carrier concentration
electron
Electrons
echoes
pump
Acoustic waves
Pumps
Incoherent scattering
pumps
excitation
ionograms
incoherent scattering
acoustics
cyclotron frequency
Cyclotrons
plasma frequencies

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Atmospheric Science
  • Astronomy and Astrophysics
  • Oceanography

Cite this

Excitation of short-scale field-aligned electron density irregularities by ionospheric topside sounders. / Kuo, Spencer.

In: Journal of Geophysical Research: Space Physics, Vol. 104, No. A9, 1999JA900232, 1999, p. 19889-19894.

Research output: Contribution to journalArticle

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