What is the Kp index and where to find it?
The Kp index is a parameter that ranges from 0 to 9 and indicates the level of geomagnetic activity, which directly correlates with aurora activity. Thus, Kp is one of the most important indicators to watch for successful aurora photography.
The 27-day aurora forecast combined with the moon phase and dark hours calendar
What is the Kp index?
When charged solar particles reach our planet, they interact with and disturb the Earth's magnetic field. These disturbances are detected by magnetometers from different parts of the Earth. Then the planetary K index or Kp index is calculated for each 3 hours interval by the GeoForschungsZentrum, Potsdam, Germany. These calculations are made twice a month and with a significant delay.
For you as an aurora photographer, Kp index forecasts and estimated Kp index provided by the NOAA Space Weather Prediction Center are much more helpful. They issue 3-day and 27-day Kp forecasts and calculate the estimated Kp index almost in real-time. You can use Kp forecasts to know what to expect and the estimated Kp index to see if the reality matches the prediction.
Why the Kp index is so important
The Kp index lets you know if you can see the aurora at the given location, where in the sky it will appear, and how bright, active, and colorful it should be. Learn more from the related posts:
What Kp you need to see the aurora
What does Kp index mean for aurora photography
Kp index and the aurora: explained from Kp0 to Kp9
Aurora forecast: what you must know
Where to find the Kp index
As mentioned earlier, the 3-day and 27-day Kp index forecasts and estimated current Kp are provided by NOAA Space Weather Prediction Center (SWPC). All the websites and apps that show you the aurora forecasts use their data. The difference is how forecasts are presented and combined with all other helpful information for aurora photography.
The 27-day Kp index forecast is published every Monday, and the 3-day Kp index forecast is updated every 3 hours. You can find the 27-day forecast and 3-day forecast on the SWPC website, but on the website the latest 3-day forecast is uploaded only every 12 hours.
Step's Aurora Guide app shows the 27-day forecast with the moon phase calendar and times when it's dark enough to see the aurora. And the 3-day forecast with weather and cloud coverage forecast. Find out more about aurora forecast and guide app.
