It operates anywhere magnetic fields pervade space--which is to say almost everywhere. In the cores of galaxies, magnetic reconnection sparks explosions visible billions of light-years away. On the sun, it causes solar flares as powerful as a million atomic bombs. At Earth, it powers magnetic storms and auroras. It's ubiquitous.
The problem is, researchers can't explain it.
The basics are clear enough. Magnetic lines of force cross, cancel, reconnect and—Bang! Magnetic energy is unleashed, with charged-particles flying off near the speed of light. But how? How does the simple act of crisscrossing magnetic field lines trigger such a ferocious explosion?
"Something very interesting and fundamental is going on that we don't fully understand," says Jim Burch of the Southwest Research Institute.