TESTING: G7IZU VLF/LF Sudden Ionospheric Disturbance Monitor
Top plot colour key:
Red: MSF 60k0 field strength
Cyan: DCF 77k5 field strength
Blue: GQD 22k1 field strength
Purple: MSF 60k0 (normalised field strength)
SIDs may appear as either positive or negative shark-fin shapes on the plot. Here, on 60 kHz, they appear as negative (upside down) fins.
Some transmitters switch off and on at various times or on a schedule (eg. DHO38 is off every morning from approx. 07-08 UT. Signal variations also usually occur for around 30 minutes at UK sunrise and sunset times and should not be confused with flare events. Flares are only very rarely detected on VLF/LF during the night-time hours. The GOES X-RAY plot (lower plot) provides confirmation of any events.
Distance from 60 kHz transmitter (Anthorn) to G7IZU ~300 miles