Lights in the Sky: What Causes Auroras?


Have you ever looked up towards the night sky and seen those bright, weird ribbons of color? If you live near the North or South Pole, you probably have! These Northern and Southern lights are called aurora. and they are what a lot of people call one of the most beautiful sights in nature. There are several types of auroras, and they can happen at any time – but what actually causes them happens to be pretty interesting.

Before we can study the different types of auroras, we need to first explore parts of Earth’s magnetic field. Our planet’s magnetic field is actually a lot like the one you would see using a typical classroom bar magnet: starting from the top of one pole, looping down, and flowing back into the other side. These looping magnetic field lines create a shield around the Earth that extends into space. If you could see them, they would look like a giant donut with small holes at the top and bottom poles.

Earth's Magnetic Field. Image Credit : Smore Science

It may sound silly, but this “donut” is the only thing keeping our atmosphere from getting stripped away by fiery solar plasma, which packs quite a punch when it interacts with Earth’s atmosphere. In fact, the Sun’s solar plasma has the power to distort the shape of our magnetic donut, squashing it on the side facing the Sun and blowing it away on the other side. But even if our donut bends, it does not break. The result of this crazy, magnificent battle is a breathtaking display of particle physics in action: auroras.

The dazzling light shows we typically see at the North and South poles have one long line of light, caused by solar winds hitting our upper atmosphere. Negatively charged particles in the Sun’s solar winds zoom across the sky, slamming into other particles in the Earth’s magnetic field. This action builds up energy. Then as the particles relax back into their normal state, that energy slowly dies and leaks out as light in a process that reflects spectacular, vivid colors. You could even say that auroras are just beautiful, cosmic graveyards where the remains of dead energy goes to rest in peace.


However, these giant curtains streaking across the sky are not the only type of aurora out there. There are also the much more common, but less bright, pulsating auroras. Pulsating auroras are different and get their name from the fact that they pulse, like a heartbeat. Even though scientists have suspected this pulsing action for almost 50 years, they have only just started being able to gather evidence.

The launch of the Arase Satellite by the Japanese Aerospace Exploration Agency in 2016 was a first step towards understanding these crazy light shows. It provided the tools to observe a clear relationship between charged particles and a new type of plasma: chorus wave plasma. This new research is important for more than just the Earth, because chorus waves have already been detected on Jupiter and Saturn!

So this is only the beginning. Learning about our home planet just opens the door to more questions about our solar neighborhood, the icy outer planets, and beyond. And when the next great discovery is made, Smore will share it with you first.


Aurora: a natural “light show” in the sky, caused by magnetic forces

Chorus waves: magnetic waves caused by charged particle collisions

Plasma: neutral particle matter

Pulsating auroras: auroras that retain energy and fluctuate in magnitude.

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