Scientific Guide to the Northern Lights

November 23, 2016

Check out my Iceland Travel Guide and my article Top Tips for Travelling Iceland in Winter.


If you don’t understand the physical phenomena that causes the Northern Lights, how you will be able to work out the best way to see them? The answer is you won’t and instead you may end up paying a tour guide a lot of money for nothing. Read this guide and the links within and you stand a much greater chance of seeing the lights. And even if you don’t see them, at least you will understand why!

The Phenomena That Causes the North Lights

The principle phenomenon that causes the aurora is the solar wind, a stream of charged particles released from the sun. A great explanation of this phenomena can be found in this video.

As these charged particles stream towards the Earth, they are affected by the Earth’s magnetic field. As the particles pass through the magnetic field they are deflected towards the polar regions. This deflection is the same phenomena that causes an electric motor to rotate.

As these particles continue to move towards the poles, they begin to lose their energy. This lost energy is converted into light which we then see as an aurora.

What affects my ability to see the northern lights?

In order to give yourself the best opportunity to see an aurora, it is worth spending a bit of time understanding the factors affect your ability to see the lights. Specifically it’s good to know which of these factors you actually have some control over!

Solar Flares and the KP Index

Solar flare activity on the sun creates the charged particles that interact with the Earth’s magnetic field and creates the aurora. It takes several days for the charged particles to reach the Earth after a solar flare ejection meaning it is possible to predict with good accuracy the level of aurora activity on any given day. This aurora activity is measured with a Kp-Index.

Cloud Cover

It doesn’t matter how strong the solar flare activity is, or how bright an aurora might be, if there are any clouds in the sky then it is impossible to see the northern lights. We have very little control over the cloud cover above our heads. On any given night, some parts of Iceland may have less cloud cover than others. Unless you can transport yourself instantly to the other side of the country, there is little you can do to avoid cloud cover.

Light Pollution

Anybody who lives in a major urban area will be familiar with ‘urban night glow’, a form of light pollution that makes it very difficult to see stars in the night sky. If you are in an area with even a moderate amount of light pollution, you will find it very difficult to see stars, the milky way or an aurora. This includes the urban area around Reykjavík.

Aurora Forecast

All of this means it is possible to make a forecast for the aurora in much the same way that you can for rain or sunshine. The best aurora forecast for Iceland can be found at Note that this forecast includes two of the factors mentioned above. The Kp Index is shown in the top right on a scale of 0-9. Cloud cover is shown superimposed on the map. Some instructions for using this forecast, if there are still some misunderstandings, can be found at

What time of the year can you see them?

First and foremost, complete darkness is required to see the northern lights. Due to the extreme latitude of Iceland, the skies do not become completely dark from the start of April until the end of August. In this period, the northern lights cannot be observed. The sky just doesn’t become dark enough. This can be clearly seen on this Reykjavík sun graph.

On a yearly basis, the solar activity that causes the lights is peaks in September and March. The reasons for this trend relate to the equinoxes. A decent explanation exists at…/aurora_live.

Combining these two facts, it is possible to see the northern lights from September until late March. However the intensity of the lights is often higher at the start and end of this window.

Tell it to me straight! What do I need to do?

  • Visit Iceland between September and late March.
  • Visit and hope for high intensity aurora with low cloud cover.
  • Get away from sources of light pollution.
  • Wait for it to get dark and look upwards.

Should I sign up for a Northern Lights Tour?

These tours are very popular in Reykjavík. If you have read through all the material on this page so far, you might understand why I am skeptical about their real value. The only thing that these tours can actually do to enable tourists to see the northern lights is to take you away from the light pollution around Reykjavík. They might take you in a nice bus, offer you hot drinks and add value in other ways. But at the end of the day, they have no control over solar flare activity or cloud cover.

My advice is that if your trip to Iceland is short and you don’t have your own transport, sign up for a tour. Otherwise avoid them, follow the steps in this guide and keep one eye on the heavens.

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