This is a closer render of the same set up.

You can see a grey line a bit up from the bottom of the ball.  This is the floor.

I suspect that playing with the settings might allow one to get a stronger effect, specifically is one could increase the strength of the glow.  This is probably done with the RayBias, but I'm not certain off hand.

A more volumous object then a flat plane might create a more obvious effect as well.

This is what I've discovered thus far.  I have to run to work now, but I will revisit this tonight.

Oh, btw, my setting are set to 'inches'.  I know that in many cases your preference settings change what the numbers mean in the material room.  If you are following someone's sample and they are using Metric but you are using Imperial, you won't get the same effect.