Why are there sometimes northern lights?
Last week, Mika and I were on vacation in Finland. When it got dark in the evening, we sat down by a large lake in the middle of the forest to look at the stars. And then it suddenly happened: The sky started to glow. At first it was a faint glow, later the lights turned green and pink, and even moved. What a spectacle! This phenomenon is called aurora borealis, or Northern lights. Mika and I had never seen anything like it before. Excited, we went back to the lake the next evening. The sky was starry and the air was freezing cold. And there we sat, waiting for the Northern lights. But nothing happened. Not the slightest glimmer of green light.
Why aren’t there Northern lights every day? And why haven’t we seen anything like this in Germany? Hannah, who was sitting next to us by the lake and had seen many northern lights before, was able to explain it to me. “Whether and where we see the northern lights has a lot to do with the sun,” she said. “The sun is a very dynamic and energetic place. Sometimes there are eruptions on the surface of the sun and lots of tiny, charged particles are spewed out into space and towards the earth. The particles, mostly protons and electrons, are also called solar wind.” Oh, and because the sun doesn’t hurl particles towards the earth every day, they don’t reliably reach us every evening. That makes sense. But how tiny, invisible particles become such beautiful lights, I wanted to know from Hannah. “The super-fast particles from the sun collide with the air particles in the atmosphere and transfer some of their energy, similar to a bumper car ride. However, the air particles can’t retain this additional energy for long and release it again – in the form of light. And depending on which air particles the solar wind collides with, different colors can be created. Oxygen, for example, is responsible for yesterday’s green.” So it wasn’t the solar particles that glowed the day before, but our atmosphere. How cool!
But one question was still very much on my mind. Why does this only happen in the north of the earth and not here in Leipzig? But Hannah had an answer to that too: “The Earth’s magnetic field is responsible for this. The particles that the sun spits out have a charge and are directed to the poles by the Earth’s magnetic field and only enter the atmosphere there. If the solar wind is particularly strong, the particles may arrive further south and collide with the atmosphere, allowing us to see the Northern Lights even in Germany.” Unfortunately, this only happens very rarely. Lastly, Hannah told us that there are also northern lights at the South Pole, only there they are called southern lights or aurora australis. But they look exactly the same.
To our disappointment, no more solar wind arrived that evening to cause the northern lights to appear over our heads. However, Mika and I now know that we should have a look at the sky at home too, maybe we’ll be lucky enough to see the Northern lights in Germany.
