Aurorae: They’re colorful, mesmerizing and, most of all, mysterious. Scientists understand the basic physics behind how charged particles interact with our atmosphere to produce these dancing lights. But the larger mechanics of when, why and how auroras appear still isn’t very well understood.
One particular mystery is that the northern and southern lights don’t always match up like researchers would expect. For years, scientists assumed that aurora borealis and aurora australis would mirror each other. That is, people in the Arctic and Antarctic Circles would see a similar show if their positions were just right. But recent research has shown that’s not the case. And now a team led by scientists from the University of Bergen in Norway thinks they have an answer.
Read more: Everything worth knowing about auroras
Life in the bubble
If you simply imagine our planet’s vast magnetic field like the classic bar magnet moving around iron filings, you’d expect Earth to have a series of symmetrical magnetic lines looping out from the surface and returning in the opposite hemisphere.
But this mental simulation leaves out one thing — the solar wind.
We don’t often see it, but we’re living inside a bubble. The ocean of molten metal in Earth’s core makes our planet into a giant magnet, which powers a sea of magnetic energy extending invisibly far out into space. That’s a good thing, too. Our Sun ejects a constant stream of charged particles that sweep past our planet. If we could see the magnetic fields, Earth would look like a tiny island in a torrent of magnetic energy. Our magnetic field pushes against the solar wind and channels it past the planet. That stops dangerous cosmic radiation from reaching the surface, and acts as a buffer against surges of electromagnetic energy from solar storms.