Black holes are known to suck anything that comes in their path -- stars, planets, you name it. However, a black hole doesn’t really possess a magnetic field of its own. Instead, it’s the dense plasma that surrounds the black hole as an accretion disk does.
As the plasma moves around the black hole, the charged particles it possesses generate an electrical current, creating a powerful magnetic effect. The direction in which the plasma flows doesn’t really change abruptly so it was assumed to be very stable.
However, now, researchers have come across evidence that a black hole’s magnetic field has its magnetic field flipped. Basically, the orientation of the magnetic imaginary poles flips.
As crazy as this sounds, this is a common phenomenon for stars and planets -- our Sun reverses its magnetic field every 11 years (what we know as the 11-year cycle of sunspots). But this wasn’t expected to be possible for black holes.
Reported first by Universe Today, researchers who stumbled across this looked at the observations of the galactic flare across the full spectrum of light from radio to X-ray. One of the things they observed was how the X-ray’s intensity faded very quickly. To the unaware, X-rays are produced by charged particles spinning in an intense magnetic field near a black hole.
At the same time, the intensity of light in visible and UV spikes hinted that areas of the black hole’s accretion disk were getting warmer, all these effects aren’t something you’d expect with a tidal disruption event, according to the researchers. They instead hypothesize that magnetic reversal aptly fits the scenario.
The team showed as a black hole accretion disk underwent magnetic reversal, the fields weaken at the outer edges of the accretion disk first, causing the disk to heat up more efficiently. Simultaneously, a weaker magnetic field means fewer X-rays are produced by charged particles. After the magnetic field reversal is complete, the disk switches back to its original state.
This is only the first observation showcasing the magnetic field reversal of a black hole. More research could help find if this is a more common phenomenon or just a one-off situation.