Globular lightning, a ball of fire or light, slowly floating in the air during the heavy storms is a very rare phenomena that stunned scientists over the decades. Long time they were considered just a myth or a psychological phenomena.
Photos of globular lightning are very rare and witness stories are often confused, raising lots of questions. For example, eye witness declared that they saw light balls in full day under clear sky, Their shape was spherical, cylindrical, water drop shape, or irregular.
There are some theories trying to explain the mystery of globular lightning. The most popular assumes that they are some stable plasma balls, due to the auto-generated magnetic fields. Plasma is a hot gas of ionized particles, but some calculations shows that the stability of this kind of structure implies high temperatures inside, and this means that plasma inside ball is very hot and should rise up in the atmosphere very quickly. No such behavior was observed until now.
Another theory claims that if a lightning bolt hits the ground, they literally melts the rock
giving birth to a hot spot of gases, where plasmatic structures and oxidation reactions coexists. In other words globular lightning is some kind of combination between a burning torch and a neon bulb (the plasma, itself).
All theories remain just theories, because until now nobody successed in replicating the phenomena in lab conditions. Until then, we still have lots of unanswered question about this strange natural phenomena.