Some examples of Sudden Ionospheric Monitoring Disturbance (SID-Monitoring) graphs from around the time of the visible aurora in Lichfield, UK, May 2024

The traces below show some SID-monitoring traces at very low frequency radio (23.4KHz) , demonstrating multiple large SIDs around the date of the incredible visible aurora borealis seen throughout the UK in May 2024.

These are some exemplar dates only – other dates showed similarly impressive SIDs. SIDs represent solar flares hitting the atmosphere of Earth and changing the ionospheric radio conduction at VLF frequencies – which results in a change in total power transmission and the typical sharks-fin patterns circled in the graphs below. These are indicative of M-class and X-class solar flares, which I have labelled on the graphs.

Andy