Nonlinear upper hybrid waves generated in ionospheric hf heating experiments at HAARP

Spencer P. Kuo, Brenton J. Watkins

Research output: Contribution to journalArticlepeer-review


Excitation of nonlinear upper hybrid waves by O-mode HF heater in the ionospheric heating experiments was explored via HAARP digisonde operated in a fast mode. The observations are manifested by a bump in the virtual spread, which expands the ionogram echoes upward as much as 140 km and is located below the upper hybrid resonance frequency. The bump is similar to that, occurring in daytime ionograms, caused by the cusp at the E-F2 layer transition, indicating that there is a small ledge in the density profile similar to E-F2 layer transitions. The ionograms also show that the virtual height spread, which exceeds 50 km over a significant frequency range below the upper hybrid resonance frequency, is downward, rather than upward as observed in a natural Spread-F situation. It indicates that density irregularities along the geomagnetic field, rather than field-aligned, were generated. Theory shows that the upper hybrid waves excited by the parametric instabilities evolve into nonlinear periodic and solitary waves that enhance downward virtual height spread and generate density cavity to explain the experimental observations.

Original languageEnglish (US)
Article number8910457
Pages (from-to)5334-5338
Number of pages5
JournalIEEE Transactions on Plasma Science
Issue number12
StatePublished - Dec 2019


  • Ionosphere
  • Jacobian elliptic functions
  • Spread-F
  • ionospheric density cusp
  • ionospheric heating and modification
  • nonlinear upper hybrid waves
  • nonlinear wave propagation
  • plasma heating
  • plasma waves
  • solitons

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Condensed Matter Physics


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