  We suggest that the ball lightning (BL) is a weakly ionized gas, in which the
electromagnetic radiation can be accumulated through the Bose-Einstein
condensation and/or the photon trapping in the plasma density well. We derive
the set of equations describing the stability of BL, and show that the BL
moving along charged surface becomes unstable. Eventually the instability leads
to explosion of BL and release of energy of the trapped photons and/or the
Bose-Einstein condensate.
