(a) HF Doppler spectrogram in the interval ~ 1600–2400 UT, 17 June 2022. The dashed rectangle shows an interval of ionospheric irregularities from ~ 1930 to 2230 UT. Wave structures are visible to the left and right of the highlighted interval. (b) Map of Nigeria showing IPP tracks of satellites crossing the vicinity of the reflection point of the HF signal, before (PRN1), during (PRN7), and after (PRN14) the irregularities highlighted in (a) occurred.