20 Jul 2023
 | 20 Jul 2023
Status: a revised version of this preprint is currently under review for the journal ANGEO.

On mechanisms for HF pump-enhanced optical emissions at 557.7 and 630.0 nm from atomic oxygen in the high-latitude F-region ionosphere

Thomas B. Leyser, Tima Sergienko, Urban Brändström, Björn Gustavsson, and Michael T. Rietveld

Abstract. The EISCAT Heating facility was used to transmit powerful high frequency (HF) electromagnetic waves into the F-region ionosphere to enhance optical emissions at 557.7 and 630.0 nm from atomic oxygen. The emissions were imaged by three stations of the Auroral Large Imaging System in northern Sweden and the EISCAT UHF incoherent scatter radar was used to obtain plasma parameter values. The ratio of the 557.7 to 630.0 nm column emission rates changed from I5577/I6300 ≈ 0.2 for the HF pump frequency f0 = 6.200 MHz ≈ 4.6 fe to I5577/I6300 ≈ 0.5 when f0 = 5.423 MHz 4 fe, where fe is the ionospheric electron gyro frequency. The observations are interpreted in terms of decreased electron heating efficiency and thereby weaker enhancement at 630.0 nm for f0 = 5.423 MHz 4 fe. The emissions at 557.7 nm are attributed to electron acceleration by upper hybrid waves of meter-scale wavelengths that can be excited with f0 = 5.423 MHz 4 fe.

Thomas B. Leyser et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on angeo-2023-21', Anonymous Referee #1, 15 Aug 2023
    • AC1: 'Reply on RC1', Thomas Leyser, 06 Sep 2023
  • RC2: 'Comment on angeo-2023-21', Savely Grach, 17 Aug 2023
    • AC2: 'Reply on RC2', Thomas Leyser, 06 Sep 2023
  • RC3: 'Comment on angeo-2023-21', Anonymous Referee #3, 21 Aug 2023
    • AC3: 'Reply on RC3', Thomas Leyser, 06 Sep 2023

Thomas B. Leyser et al.

Thomas B. Leyser et al.


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Short summary
Powerful radio waves transmitted into the ionosphere from the ground were used to study electron energization in the pumped ionospheric plasma turbulence, by detecting optical emissions from atomic oxygen. Our results obtained with the EISCAT (European Incoherent SCATter association) facilities in northern Norway and optical detection with the ALIS (Auroral Large Imaging System) in northern Sweden suggest that long-wavelength upper hybrid waves are important in accelerating electrons.