OR!
In the corona the electrons from the hydrogen atoms are seperated by greater distances (plasma), so when the electron (and then a miracle happens) jumps back closer to the nucleus it releases a higher energy photon.
C’mon, how complicated can it get, were dealing with just hydrogen.
Re: just Hydrogen
Any element can form a plasma... just get it hot or charged enough.
Electrons in a plasma are disassociated from the nucleus and can be thought of as free electrons, easily moved through the plasma which is what makes a plasma a good conductor.