In this thesis the problem of energetic particle (electrons and ions)
acceleration by an ensemble of shock waves is addressed.
Shock waves are generated,
moving randomly, inside a turbulent flow (e.g. jets and
hot spots of extragalactic radio sources) or in an involving and constantly
changing active region on the Sun. The acceleration is based on the
`shock drift mechanism' using the adiabatic treatment. The
transport and the radiation of the particles in stochastic magnetic fields
is also studied.
The resulting energy distribution of the energetic particles
is calculated analytically and numerically,
after their interaction with a number of shock waves. Two
models are presented,
the first one is an application to the solar flare problem
and the second
one is applied to the hot spots of extended extragalactic radio sources
The comparison of
the results with the observations leads to a good agreement.