Numerical study of upper hybrid to Z mode leakage during electromagnetic pumping of groups of striations in the ionosphere

B. Eliasson, T. B. Leyser

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We investigate numerically the interaction between ionospheric magnetic field-aligned density striations and a left-hand circularly polarized (L)-mode wave. The L-mode wave is scattered into upper hybrid (UH) waves which are partially trapped in the striations, but leak energy to electromagnetic waves in the Z-mode branch. For small-amplitude (1 %) striations, this loss mechanism leads to a significant reduction in amplitude of the UH waves. For several striations organized in a lattice, the leaking of Z-mode waves is compensated by influx of Z-mode radiation from neighboring striations, leading to an increased amplitude of the weakly trapped UH waves. For large-amplitude (10 %) striations the trapped UH waves rapidly increase in amplitude far beyond the threshold for parametric instabilities, and the Z-mode leakage is less important. The results have relevance for the growth of striations and the onset of UH and lower hybrid turbulence during electromagnetic high-frequency pumping of ionospheric plasma, which require large-amplitude UH waves.
Original languageEnglish
Pages (from-to)1019-1030
Number of pages12
JournalAnnales Geophysicae
Publication statusPublished - 19 Aug 2015


  • upper hybrid waves
  • Z mode waves
  • striations
  • ionosphere

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