Radio aurora
During a geomagnetic disturbance, charged particles excite the atmosphere near the auroral oval and create columns of ionisation that scatter VHF signals. Operators point their antennas north (in the northern hemisphere) and work stations whose signals bounce off the aurora. Signals sound raspy and distorted, so CW and SSB are the usual modes, and the effect is stronger on 6 metres than on 2 metres.
The higher the Kp index, the further south (or, in the southern hemisphere, north) the oval reaches. A rough rule: the equatorward edge of the oval sits near 67° minus about 1.9° per Kp step in geomagnetic latitude. Kp 5 or more makes aurora likely at mid-high latitudes. The live band conditions page shows the current estimate.
Sporadic-E
Sporadic-E (Es) is the formation of dense, thin patches of ionisation in the E layer. It can reflect 28, 50 and sometimes 144 MHz signals over 1000 to 2500 km in a single hop. In the northern hemisphere the main season runs from May to August with a secondary peak around December and January. Es is hard to forecast and does not correlate well with solar indices, so the site shows seasonal likelihood rather than a live prediction.
Tips
- Watch for 10 metres and 12 metres Es first: it often opens before 6 metres does.
- Use a beacon or a cluster of spots to confirm an opening in progress.
- For aurora, check the Kp forecast and listen when Kp rises quickly.
