First of all use a soft brush set at about size 150, and make a white blob in the middle of a black canvas.
Now add a color balance with these settings:
Shadows: +94, +4, -100
Midtones: +77,0,-71
Highlights: +20, +2, -45
(preserve luminosity unchecked).
Now gaussian blur it with 6.0 Pixels.
Now smudge the center to the bottom left slightly, and then smudge the back to the top right, to create a motion effect.
Now to give it a really nice effect add a black and white gradient map set to overlay and sharpen the fireball layer.
Hope you enjoyed!
