The figure shows the two-dimensional projection in GSE x–y coordinates of the traces of the north (blue) and south (red) auroral ovals, each assumed here to lie between lines of constant altitude adjusted corrected geomagnetic (AACGM) latitude from 65–75° during matching UT times for northern summer (a; 21 June 2016) and northern winter (b; 21 December 2016) solstices. The solid and dashed black lines denote the loci of the edges of the ovals in the northern and southern hemispheres as a result of diurnal rotation during the northern summer (a) and winter (b) solstices. The bold solid black circle at high latitudes denotes the locus of the geomagnetic poles. The solid vertical line denotes GSE x = 0 mark/the terminator. The area in Earth’s shadow is shown in grey.