Topics Earth, weather and climate

What causes the northern lights?

The northern lights, or aurora borealis, are caused by charged particles from the Sun colliding with gases high in Earth's atmosphere. Earth's magnetic field steers many of those particles toward the polar regions, where they strike oxygen and nitrogen. The excited atoms then give off some of that energy as light, which we see as green, red, pink or violet curtains.

What makes it interesting is how many steps are chained together. The Sun constantly sends out a stream of charged particles called the solar wind, and sometimes it throws out a much bigger burst. Earth's magnetic field acts as a funnel, which is why the lights usually gather in rings around the poles. The colors depend on which gas is struck and how high up it happens. Some details, such as exactly how particles gain their energy before they hit, are still studied by space scientists.

An episode would follow one particle from the Sun to the glow, then ask why the show is stronger some years than others, why the south has its own version, and what a solar storm can do to satellites and power grids. It would also cover how to improve your odds of seeing them. bre's hosts are AI, so they can make mistakes, and you can press Talk to ask a question along the way.

What a bre episode would cover

An outline of the episode bre would make for this question. Every episode is written fresh when you ask, so yours will differ.

  1. The Sun's constant breezeThe Sun releases a stream of charged particles called the solar wind, and now and then a far bigger burst. This is where every aurora begins.
  2. Earth's magnetic shieldEarth's magnetic field deflects most of the solar wind and guides some particles toward the poles. That is why the glow forms rings around them.
  3. Atoms lighting upIncoming particles hit oxygen and nitrogen high above the ground and excite them. The atoms release some of that energy as light, while other energy ends up as heat or other processes.
  4. Why green, red and purpleOxygen and nitrogen glow in different colors, and altitude changes what you see. Green is the most common, with red higher up.
  5. Solar cycles and big stormsThe Sun's activity rises and falls over roughly eleven years. Strong storms can push auroras far from the poles and disturb satellites and power systems.
  6. The southern lights and other planetsThe same process makes the aurora australis around the south pole. Planets with magnetic fields, such as Jupiter and Saturn, have auroras too.
  7. How to actually see themDark skies, clear weather, high latitudes and space weather forecasts all help. Even then, nothing is guaranteed.

How the episode might open

A sample exchange between two of bre’s AI hosts, bre and Cal. Both are AI; this is written by AI, as every bre episode is.

  1. breAI host

    The northern lights look like they belong to the sky, but the story starts at the Sun. So what actually leaves the Sun, and why does it end up glowing over Norway?

  2. CalAI host

    Charged particles, streaming out all the time. We call it the solar wind, which sounds gentle, but it's a flow of stuff moving at roughly hundreds of miles per second, and Earth just sits in it and shrugs.

  3. breAI host

    It shrugs because of the magnetic field. Earth is basically a big magnet, and that field bends most of those particles away. Some get steered toward the poles, which is why the lights usually show up in rings up north, and only rarely over somewhere like Texas.

  4. CalAI host

    So the planet is a fridge magnet with a PhD. Okay, but the particles are tiny. Hold on, how does that actually work? How does something that small make a glowing curtain?

  5. breAI host

    Okay, here's the part nobody tells you. The particles don't glow. They slam into oxygen and nitrogen way up high, and that knocks those atoms into an energized state. When they settle back down, they give off light.

  6. CalAI host

    So it's like a neon sign. Electricity goes in, gas lights up.

  7. breAI host

    Similar idea, since energized gas gives off light. But the energy comes from solar particles slamming into the atoms, not from an electric circuit. Some of it becomes light, and the rest goes into heat and other processes.

  8. CalAI host

    So the magnet funnels the particles toward the poles, the particles hit the gas, and that's why the glow sits in rings up there.

  9. breAI host

    Right. Sun, magnetic field, thin air up high, and a curtain of light near the poles.

Questions people also ask

Why are the northern lights green?
Green usually comes from oxygen atoms glowing at moderate heights in the upper atmosphere. Higher up, oxygen can glow red, and nitrogen can add blue or purple edges. The mix of colors depends on which gas is hit and at what altitude.
Can you hear the northern lights?
Not in the usual way. The aurora forms roughly 60 miles or more up, and ordinary sound from there would not reach the ground. Some people report faint noises during displays. What causes them is still debated and not fully settled.
Can you see the northern lights from the United States?
Sometimes. They are most often seen in Alaska and northern Canada. During strong solar storms they have been seen much farther south, though that is rare. Space weather forecasts give an idea of when a bigger display might happen.
Are the northern lights and southern lights the same thing?
Yes, they are the same process. Solar particles guided by Earth's magnetic field strike the upper atmosphere near each pole. The northern version is the aurora borealis and the southern version is the aurora australis. They are driven by the same solar activity and can brighten around the same time.

Related topics

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bre’s hosts are AI, and every episode is generated, so they can be wrong: check anything that matters. This page outlines what an episode would cover. It is for interest and learning, not medical, financial or legal advice.