  Cosmic magnetic structures have in common that they are anchored in a dynamo,
that an external driver converts kinetic energy into internal magnetic energy,
that this magnetic energy is transported as Poynting flux across the
magnetically dominated structure, and that the magnetic energy is released in
the form of particle acceleration, heating, bulk motion, MHD waves, and
radiation. The investigation of the electric current system is particularly
illuminating as to the course of events and the physics involved. We
demonstrate this for the radio pulsar wind, the solar flare, and terrestrial
magnetic storms.
