  Based upon experimental observation in the laboratory, we propose that ionic
wind from corona discharge inside a thundercloud would play an important role
in producing a rain gush. A cyclic chain of events inside a super-saturated
environment in a thundercloud is proposed, each event enhancing the successive
ones until lightning occurs. These successive events are collision between
snowflakes and rimers, charge separation, corona discharge, avalanche
ionization, ionic wind originating from the positively and negatively charged
masses of cloud, vortex motion and turbulence when mixed with the updraft, more
collision, more charge separation, stronger corona discharge, and so on.
Meanwhile, avalanche ionization would produce more CCN (cloud condensation
nuclei) resulting in more precipitation and hence rimers formation in the
super-saturated environment. More collision in the buoyant turbulence would
lead to more fusion of droplets and the formation of larger rimers. The cyclic
processes would repeat themselves until the electric field between the two
oppositely charged masses of cloud was strong enough to induce a breakdown. The
latter would create a sudden short circuit between the two charged masses of
cloud neutralizing the charges. There would be no more ionic wind, hence, much
less buoyant turbulence. The updraft alone would not be sufficiently strong to
support larger rimers which would fall down 'suddenly' to the earth surface as
a rain gush.
