Fig. 3

A contour plot of the echo occurrence rate versus the solar local time for a Inuvik (INV), LT = UT − 7 and b Dome-C East (DCE), LT = UT + 10, SuperDARN radar observations in 2013–2017. Data at all radar operating frequencies were considered. The echo detection zones are depicted in Fig. 1a, b. Solid white lines are contours of the local solar zenith angles of 90° and 105°