It’s nice to have firsts!
Yesterday afternoon the planetary K index (https://www.swpc.noaa.gov/products/planetary-k-index) rose from a dormant Kp=1 to a healthy Kp=7.
Kp characterises geomagnetic storms.
In parallel, the aurora-predicting geomagnetic disturbance level went from green to amber and then red, breaching the 200nT threshold at about 15:30 UTC (https://aurorawatch.lancs.ac.uk/plots/?project=awn&site=sum&date=2021-05-12).
So, I turned the newly installed 6 metre Yagi north. And there was a radio aurora in full swing with MM5DWW on Orkney working the world - or at least those north of 55 degrees. We exchanged 5/7 both ways and went on our way - him to work yet more, and me to listen to a couple of CW stations. There were also some ethereal voices that might - or might not - have been other SSB stations.
My Great Circle distance to Orkney is 400km, but the actual path length will have been significantly more to the scattering medium further north and back to Orkney. In an aurora, all stations generally beam north.
The radio aurora was gone by 16:30 and 6 metres reverted to its normal flat state.
I’d heard radio auroras as a teenager but never had the necessary kit to work them, so it was good to tick that box. I’ve now got a feeder run and Yagi to install for 2 metres, so next time I’ll be able to compare the bands.
And next time I’ll remember to record the activity. The voices are heavily distorted by the Doppler shift caused by the movement of the free electrons in the auroral columns doing the reflecting. You’ve to listen hard. There’s no time for exchange of pleasantries.
Radio auroras are infrequent. Sometimes, they are intense enough and at a low enough latitude to support southern stations. If you're interested, install the AuroraWatch and SpaceWeatherLive apps.