OT:
If you have a square wave of height 10cm, going left, say. And a square wave of 15 cm, going right.
When the waves begin overlapping, you get a height of 25cm (they add linearly means 10+15=25) where they overlap. After the waves pass, you end up with a 10cm wave on the left and a 15 cm wave on the right, still the same shape.
IE: the waves do not affect each other, since after the "interaction", the waves are still the same as they were before.
For an animated example See:
http://Users.erols.com/renau/wave_interference.html
Ball lightning sounds like a plasma of N2/O2 sustained by a concentration of microwaves or just slowly fading away after being generated(by lightning, say).
No matter the source, it is hardly pure energy, since it operates in an atmosphere.
BTW plasma is not pure energy, either, it is just really hot matter, such that the electrons have been stripped away from the nuclei, and it forms a soup of electrons and protons.