provided by the Icelandic MET office
How to read the northern lights forecast
Here is how the northern lights forecast works. Let´s start with the colors. On the map you can see white areas, light green and dark green. The white color in the northern lights forecast means no clouds and that is the color we want to see. Light green means partly cloudy or not very cloudy, but dark green means very cloudy so we don´t want to see the areas dark green. The reason why we want to have the areas without clouds (or light clouds) is because it is impossible to see the lights when the sky is covered with clouds. When it is partly cloudy (light green areas) you still have a chance seeing the lights by finding a gap in the clouds. To know how active the lights are each night you look at the numbers in the upper right corner. The numbers are from 0-9 and each number is a combination of how probable the lights are to come out and how active they will be when they do. The numbers don´t say what time they show up and for how long. Therefore you can start hunting for them as soon as it gets dark. Even though the forecast is on 1-2 and says low, it is still worth going out to hunt for them if the sky is clear or with little clouds as this is only a forecast and you always have a chance of seeing them. It doesn´t hurt to try and when you see them dance, it is fully worth the wait! Last but not least, the forecast is updated around 6 pm daily so keep a close eye on the forecast daily to be updated! For understanding when in the winter it is best to come see the lights then read this article.
How are they monitored and expressed?
Satellites are the main tool for observing and monitoring the Sun and particles fluxes heading for Earth. Without them it would be difficult to do a reliable northern lights forecast. The National Oceanic and Athmospherice Admin of the USA (NOAA) operates couple of these, both for the back side and the front of the Sun. The satellites both generate images and have sensors for observing particle fluxes from the Sun. By using these observations we are able to create northern lights forecasts based on numerical simulations and forecast models. One of the most important element in these forecast models is that the Sun rotates about its axis in about 27 days, so any longer disturbances on the surface are repeated only every 27 days.
The above northern lights forecast from the Icelandic MET office is expressed on the quasi-logarithmic Kp-index as most other northern lights forecasts in the world. It is a numerical scale from 0 to 9. About 90% of the time it is 0-4 and very rarely reach 7-9 or only 1% of the time.
What are the northern lights?
The northern lights (aurora borealis) can be found both in the southern and the northern hemispheres and are a truly amazing natural phenomenon. The lights can rarely been seen outside of the polar areas but it can happen e.g. the lights have been seen down in the New York City. The southern lights have the name aurora australis. The sun is the origin of the auroras. On its surface solar activity ejects a cloud of gas, sometimes called coronal mass ejection (CME) by scientists. This cloud of gas takes normally 2-3 days to reach Earth´s magnetic field. When it collidies with this invisible field it causes complex changes to happen in the tail region of the field. Currents of charged particles are generated that flow then along the lines of the magnetic forces all the way into the Polar Regions. In the upper atmosphere these particles are boosted with energy, and when they collide with the oxygen and nitrogen atoms, the beautiful northern lights can be seen.