A new type of Doppler velocity fluctuations in HF ground scatter from the polar cap

作者：Scoular G; Ponomarenko P V^*; St Maurice J P

来源：Geophysical Research Letters, 2013, 40(19): 4992-4997.

DOI：10.1002/grl.50960

• ULF waves
• SuperDARN
• HF radar
• Pc3-4
• polar cap

We report a new type of variations in Doppler velocity of HF ground scatter echoes from the polar cap at f approximate to 10mHz. Similar fluctuations from lower latitudes are usually associated with large-scale dayside Pc3-4ULF waves. However, the polar cap oscillations exhibit a puzzling anisotropy in spatial coherence along and across the radar%26apos;s line of sight. Furthermore, in contrast to Pc3-4 waves, these fluctuations show no ground magnetic signatures and display a pronounced gap in power/occurrence around local noon. We hypothesize that localized, 100km, auroral particle precipitations near the radar site can modulate Doppler shift of the radio waves entering the ionosphere. In the ground scatter returns, due to the geometrical spread of the rays propagating through the ionosphere to the ground, these variations would appear to have a much larger line-of-sight scale.

• 出版日期2013-10-16