How to Die in Space: A Journey Through Dangerous Astrophysical Phenomena

by Paul Sutter

you can image the chaos as gas collides with itself, meets resistance, fights back, raises plumes of hotter material, drops balls of slightly cooled clumps. It’s messy. And if a big blob of gas happens to rise up out of the accretion disk, it carries with it a chunk of magnetic field lines. One part of this new lump of magnetic field will be closer to the black hole, and one will be further, because that’s how randomness works. But the bit of field line that’s anchored to the disk closer in has a faster orbit, doesn’t it? It does, good job. That extra lump of field gets stretched, pulled, and eventually wound back down into the main field of the accretion disk. And here’s your dynamo at work: it converts random turbulent motion—energy in the accretion disk itself—into ever-stronger magnetic fields. As more gas finds its way onto the disk, the fields grow more powerful. Nifty.4 For extra deliciousness, here’s the name of this particular effect: the alpha-omega dynamo. Sounds impressive, and people will think you’re smart if you say it out loud. Now here’s why I care so much about these magnetic fields, and why you should care, too. When magnetic fields are weak, you move them. When they’re strong, they move you.