Why is the sun's surface temperature around 10,000 F while the sun's corona is around 12,000,000 F?
"I absorb energy like a sponge everywhere I go. It allows me to see the world and my purpose in it." Zak Bagans, Ghost Adventures (INFJ)
Huh, I was watching a show yesterday, Science Britannica, that asked the very same question at one point. Nobody knows for sure yet. Have a look at this:
It is believed that the cause of the increased temperature is due to magnetohydrodynamic (MHD) waves that distribute the energy generated below the star's surface to the outer layers of the Sun's atmosphere.