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Occurrence rates of SuperDARN ground scatter echoes and electron density in the ionosphere
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  • Alexander V. Koustov,
  • Sydney Ullrich,
  • Pavlo V. Ponomarenko,
  • Mehdi Ghalamkarian Nejad,
  • David R. Themens,
  • Robert G. Gillies
Alexander V. Koustov
University of Saskatchewan

Corresponding Author:[email protected]

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Sydney Ullrich
Department of Physics and Engineering Physics
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Pavlo V. Ponomarenko
University of Saskatchewan
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Mehdi Ghalamkarian Nejad
University of Saskatchewan
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David R. Themens
University of Birmingham
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Robert G. Gillies
University of Calgary
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Ground scatter (GS) echoes in Super Dual Auroral Radar Network (SuperDARN) observations have been always expected to occur under high-enough electron density in the ionosphere providing sufficient bending of HF radio wave paths toward the ground. In this study we provide direct evidence statistically supporting this notion by comparing the GS occurrence rate for the Rankin Inlet SuperDARN radar and the F region peak electron density NmF2 measured at Resolute Bay by the CADI ionosonde and incoherent scatter radars RISR-N/C. We show that the occurrence rate increases with NmF2 roughly linearly up to about ~4·1011 m-3, and the trend saturates at larger NmF2. One expected consequence of this relationship is correlation in seasonal and solar cycle variations of the GS echo occurrence rate and NmF2. GS occurrence rates for a number of SuperDARN radars at middle latitudes, in the auroral zone and in the polar cap are considered separately for daytime and nighttime. The data indicate that the daytime occurrence rates are maximized in winter and nighttime occurrence rates are maximized in summer for middle latitude and auroral zone radars in the Northern Hemisphere, consistent with the Winter Anomaly (WA) phenomenon. The effect is most evident in the North American and Japanize sectors, and the quality of WA signatures deteriorates in the European and, especially, in the Australian sectors. The effect does not exist in the South American sector and in the polar caps of both hemispheres.