Our new aurora forecast will let you know, up to 3 days in advance, what your chances are of seeing the northern lights where you are. Check out the aurora forecast under the "Nearby" tab and see if there is aurora activity in your area.
In this article, we will share a little about how the aurora forecast works.
KP index and geomagnetic latitude
Did you know that the aurora borealis are a result of solar winds that disrupt the earth's magnetic field? Whether it is possible to see the aurora depends on several factors; how strong the solar wind is, where on the globe the location is situated and how clear the skies are. And of course, it must be dark outside.
The strength of the geomagnetic disturbance, and thus the probability of seeing the aurora, is given as a Kp index. This index is a scale from 0 - 9. Kp index 0 means low activity, while Kp index 9 means that an intense geomagnetic storm is underway. So the higher the number, the greater the probability of seeing the aurora.
The Kp index also describes how far towards the equator it will be possible to see the aurora. It is the combination of the Kp index and your geomagnetic latitude that will indicate how good an opportunity you have to see the aurora.
The illustration was taken from the Norwegian Center for Space Weather (NOSWE)
Threshold values and the aurora index
The aurora will not always appear when we expect it and it can often be that the light show comes and goes during the period when a strong aurora is expected. The aurora forecast will therefore be a good indication of when you may want to go out and look up, but not necessarily be a guarantee that you will be able to see the light show.
To make the aurora forecast on Yr as easy to use as possible, we have included some of that uncertainty in our aurora index. Preliminary feedback from testing shows that it will require a lot of magnetic disturbance before we can observe what can be described as high aurora activity.
In the tables below, we show how the latitudes provide threshold values for the Kp index, and how we have devised a 3-part aurora index based on this. You will find the terms in the table to the right in the aurora forecast on Yr.
The left table shows latitude and the required Kp index. The right table shows the aurora index.
Cloud cover and light pollution
The best conditions for seeing the aurora are when the sky is dark and clear, without clouds. The graph therefore gives you a good overview of cloud cover throughout the forecast period, and shows you when it is too bright to see the northern lights.
The total cloud cover is also given as a percentage and says something about how much of the sky is covered by clouds. The cloud cover can consist of clouds at different heights - as shown with different shades of gray in the graph. It is worth noting that a high cloud layer can often be transparent, and it may therefore be possible to see the northern lights through it. Low clouds are often dense and will be more of a hindrance when it comes to seeing the northern lights.
Even if there are a lot of clouds, holes can still occur in the cloud cover which makes it possible to see the northern lights if you are lucky!
Remember that light pollution can affect conditions. Therefore, it is advisable to go out to areas where there are as few street lights and other light sources as possible.
The aurora forecast is a new product from the Yr team, and we will continue to work with the accuracy of the forecasts. We have access to some observations that can help us with this, but we also want feedback from our users. Both when the forecast seems accurate and when it misses the mark. Feel free to send a feedback to firstname.lastname@example.org with information about where you are, what time you used the forecast and what you could observe in relation to what was forecast.