Fig. 18
From: Review of the accomplishments of mid-latitude Super Dual Auroral Radar Network (SuperDARN) HF radars
Observations of the altitude of the irregularities associated with SAIS from beam 12 of the Blackstone radar near local midnight on 18 November 2010. The two solid curves mark the region where the magnetic aspect angle is within 1° of perpendicularity. Reproduced from Fig. 7 of de Larquier et al. (2013)