The Corona Is Hotter Than the Sun's Surface

The sun itself is not one temperature, right? Like the core of the sun is super duper duper hot because that's where all the fusion is going on. But as you get closer to the surface, it sort of cools off and then starts to get hotter again. It's like having a light bulb where the air around the light bulb is hotter than the surface of the light bulb itself. How that gets so hot and how it stays so hot has been a mystery for more than 100 years.