Fireball Spell Effect

At first, sorry my bad english!

Well, I was thinking about the fireball spell. (fireball spell is a fireball flying as an arrow, lefting a stella like a commet, but shorter).

This is only an idea. I don’t have implemented yet.

I want do it as fast as possible, but seem espectacular.

My first idea is, for the ball of fire, draw an image on a paint program (GIMP as example), and create an alpha layer for it, more transparent into the center. Then, I have a point, which is the center of the image. Then, you can see it from every place
you want, you always see a circle (the image). Then, rotating the alpha layer different from the rgb layer, we can simulate the fire moving on. If not, we can add another image over the first, rotating alike the first.

Making the ashes, I have thought to make a particles system. I generate a small number of particles rounding the fake sphere, every one with different velocity, colour and life.
Particles go farther from sphere, but their lives are very short (less than a second).
That particles have hot colours (red, oranges, yellows), but if fireball is moving, the particles from rear of the moving must be the true ashes, and the must have a longer life, and must have gray colours.
To do this, I thought to consider a cone of 45 grad. x 45 grad. x corola rad. against the moving direction, and all particles in the cone will be ashes types and not glow type.

If some have understand this text, and know a better way to do this, please tell me how.
(a better way is more faster with the same realistic, or more realistic with the same processor cost).

This isn’t really an answer, but one idea for your fire particles - if you use a colour like maybe (0.4,0.2,0.1) with additive blending… the particles will look red… but when a few of them overlap, it will go yellow (Red hits 1.0, green keeps adding up). And if there’s really a lot of them overlapping, it will go towards white. Nice for a fire effect.