The Fire Rainbow: An Astonishing and Rare Marvel of Nature
To name it properly, a fire rainbow is a circumhorizontal arc. It is also known as a circumhorizon arc but whichever you chose, scientists (and aficionados) call it a CHA. It is given its name because it looks as if a rainbow has spontaneously combusted as it made its way across the sky.
Contrast with the circumzenithal arc (upside-down rainbow)