Aurora Visibility

What it does

Estimates how strong a geomagnetic storm (Kp index) you would need to see aurora from your location, shows tonight's dark window, and pairs that with the live Kp reading from NOAA.

What you need

A location, set with the location picker at the top. The estimate and dark window are calculated on the device. The Aurora Forecast Map and the live Kp reading need a network connection. If either cannot load, the rest of the screen still works.

How to use it

1. Set your location.
2. Optionally change the date in Date, using the date field or the step buttons.
3. Read the Result card.
4. Check the Aurora Forecast Map (NOAA's forecast image for your hemisphere).

Reading the results

• Geomagnetic Latitude: your latitude measured from the geomagnetic pole, in degrees N or S.
• Kp Needed: an estimate of the Kp level required from your location, shown as a tier with a number, for example "Possible (Kp 3+)". Tiers run from Very Likely and Likely through Possible and Unlikely to Rare.
• Tonight's Dark Window: the astronomical twilight period. In polar day or night the app says no astronomical twilight occurs.
• Moon Interference: the Moon's illumination. At 50% or more, the app notes it may wash out faint aurora.
• Live Kp (NOAA SWPC): the current Kp and tonight's forecast Kp, shown as "Current X · Tonight Y". This is a planetary value, so it does not change with your location or the selected date. It shows Unavailable if the data cannot be fetched.

When tonight's forecast Kp meets or exceeds the Kp Needed estimate, the app adds a note that aurora may be visible.

Tips

• Kp Needed is a typical estimate, not a guarantee. Strong storms can reach further.
• Face the geomagnetic pole, away from light pollution, during the dark window.