A X1.0 class X-ray flare occurred on 2021/10/28. Solar Energetic Particles have been recorded by GOES and Stereo. The polar stations of the Global Neutron Monitor Network have seen a sudden, but moderate, increase in cosmic ray count rates. The event has also been detected on Mars.
The Athens GLE Alert system has recorded an ALERT for Fort Smith (FSMT) and the South Pole (SOPO and SOPB) stations at 16:09UT. A pilot in Canada was probably the first human to detect GLE73.