Experimental data during post-sunset hours, 22 June 2022. (a) IPP tracks of PRNs 7 and 20, which registered highest S4 index near the dip equator, are marked by the red and blue arrows, respectively. (b) The signature of a plume in the HF Doppler spectrogram is indicated by the black arrow. The time of occurrence of the plume coincides with the time when elevated S4 indices were detected by the satellites.