Solar Influences on the Return Direction of High-Frequency Radar Backscatter

Angeline G. Burrell, Gareth W. Perry, Timothy K. Yeoman, Stephen E. Milan, Russell Stoneback

Research output: Contribution to journalArticlepeer-review

7 Scopus citations


Coherent-scatter, high-frequency, phased-array radars create narrow beams through the use of constructive and destructive interference patterns. This formation method leads to the creation of a secondary beam, or lobe, that is sent out behind the radar. This study investigates the relative importance of the beams in front of and behind the high-frequency radar located in Hankasalmi, Finland, using observations taken over a solar cycle, as well as coincident observations from Hankasalmi and the Enhanced Polar Outflow Probe Radio Receiver Instrument. These observations show that the relative strength of the front and rear beams is frequency dependent, with the relative amount of power sent to the front lobe increasing with increasing frequency. At the range of frequencies used by Hankasalmi, both front and rear beams are always present, though the main beam is always stronger than the rear lobe. Because signals are always transmitted to the front and rear of the radar, it is always possible to receive backscatter from both return directions. Examining the return direction as a function of local time, season, and solar cycle shows that the dominant return direction depends primarily on the local ionospheric structure. Diurnal changes in plasma density typically cause an increase in the amount of groundscatter returning from the rear lobe at night, though the strength of this variation has a seasonal dependence. Solar cycle variations are also seen in the groundscatter return direction, modifying the existing local time and seasonal variations.

Original languageEnglish (US)
Pages (from-to)577-597
Number of pages21
JournalRadio Science
Issue number4
StatePublished - Apr 2018
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics
  • General Earth and Planetary Sciences
  • Electrical and Electronic Engineering


  • SuperDARN
  • ground backscatter
  • groundscatter
  • high-frequency radar
  • ionospheric propagation
  • long-term variations


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