A comparison of satellite scintillation measurements with HF radar backscatter characteristics

We examine the correspondence between high latitude ionospheric scintillation measurements made at 250 MHz with the occurrence of 10 MHz HF coherent radar backscatter, on 13 and 14 December 2002. We demonstrate that when the ionospheric intersection point of the scintillation measurements is co-located with significant HF radar backscatter, the observed scintillation, quantified by the S4 index, is elevated. Conversely, when the radar indicates that backscatter is observed away from the intersection point due to movements of the auroral zone, the observed scintillation is low. This suggests that scintillation is highly locationdependent, being enhanced in the auroral zone and being lower at sub-auroral latitudes. The coexistence of scintillation and HF radar backscatter, produced by ionospheric density perturbations with scale sizes of 100 s of metres and ∼15 m, respectively, suggests that a broad spectrum of density fluctuations is found in the auroral zone.