When magnetic fields around a black hole reconnect, they can slow down plasma particles near the event horizon, which cause the black hole to lose energy when it swallows them
Source:
https://www.newscientist.com/article/2264389-black-holes-leak-energy-when-they-eat-plasma-near-the-event-horizon/?utm_campaign=RSS%7CNSNS&utm_source=NSNS&utm_medium=RSS&utm_content=home