What you did not know about the northern boreales

Associated with the poles and the magic of Lapland, the northern lights have tickled our imagination since the dawn of time. But do you know where these fabulous luminous streaks come from?

They are pink, red, green, yellow, and challenge the night sky with their mysterious undulations. If you were lucky to observe, you are not ready to forget it! But where do the northern lights come from, and where to observe them? We decipher the subject with an expert.

4 questions to an astrophysicist

Marie Dominique, astrophysicist at the Royal Observatory of Belgium, explains this phenomenon to us.

What is a boreal aurora and how to explain it?

An aurora borealis is a natural light phenomenon caused by the ejection of particles by the sun. You should know that the sun emits protons and electrons via 2 mechanisms:

• The 1^East is the solar wind, more or less permanent, but whose intensity fluctuates. When the dawn are due to this mechanism, they remain mainly confined to areas close to the poles, both in the north and in the south. And this, because the configuration of the terrestrial magnetic field at the level of the poles creates a passage for these particles.
• The 2^e phenomenon, these are coronal mass ejections. When the sun erupted, it happens that it spits a cloud of particles from its crown and that this cloud reaches the earth. These particles can take with them the magnetic field of the sun. However, if it is not oriented in the same way as that of the earth, this causes a geomagnetic storm which extends the area in which the aurora are visible. This explains why we can see them with us too …

Where and when to observe northern lights?

They are observed in what are called the auroral oval, which corresponds approximately to the polar circle, therefore an area between 65 ° and 75 ° latitude in the north as in the south. This covers northern Norway, Sweden, Finland, Canada, Russia …

As for the period, the most beautiful dawn are those associated with solar eruptions. Their frequency varies over time, following a cycle of about 11 years. We have just passed the peak, but we are currently in a suitable period to observe it.

It must be black, the ideal is therefore to go to the far north in winter, where night lasts several months, between October and March. Finally, the sky must be cleared, and if possible that one is far from the cities to avoid light pollution. Afterwards, all you have to do is cross your fingers …

Is it possible that we observe northern boreales in our regions next winter?

Yes, but to do this, these dawn would have to be linked to important sunscreen. In May 2024, there were very beautiful solar eruptions in Belgium. They had been numerous, important, and had followed at an exceptional rate. In a fortnight, there had been about twenty eruptions. By way of comparison, between January and July 2025, we only had a large scale of it… Result: we observed beautiful northern lights from our regions. There is still a chance that we can do it next winter, but it is not as likely as in polar areas.

What influences the color of the boreal aurora?

What determines the color of the boreal dawn is the type of atmosphere molecule that interacts with the solar particles. Oxygen, for example, at very high altitude, produces red light and low altitude, green light. Mauve is rather produced by nitrogen. Then, the boreal aurora covers a wide range of altitude. Depending on its height or the distance to which it is observed, its appearance will be different. The beautiful usual green structures are rather produced at low altitude. We see them better if they are just above us. If we see the dawn too far or in profile, we will see only the summit.

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