Map of the ionospheric irregularities measured around 22:00 UT of January14th over the European sector at latitudes between 45° and 80° N and longitudes between −15° and 25° E. The red lines represent the boundaries of the auroral oval modelled by the DMSP. The ROTI data are represented in the yellow–black scale if over the threshold of 0.2 TECU/min or as simple gray dots if under it. The LOFAR S4 follow the same logic with a threshold of 0.05 and a scale green/blue and red “x”.