Physics of potentially geoeffective solar phenomena

   The Sun is a major factor controlling geophysical fields from the Earth's
   magnetosphere down to the atmosphere. While the major influencing factors
   will be reviewed shortly a special emphasis will be put on eruptive
   phenomena. Current observations by space telescopes and numerical modeling
   efforts have brought new insights into the physics of eruptive phenomena.
   In particular the role of magnetic reconnection will be discussed.
   Reconnection releases magnetic energy emerging from inside the Sun,
   accelerates particles to high energies and plasma into the solar wind.
   Finally, reconnection feeds solar energy also into the geosphere. The
   observed energy releases usually are, however, usually, unsteady, even
   bursty. Despite of early models reconnection seems to be very
   non-stationary, unsteady process. A theoretical description is given of
   the underlying physical processes which might be developed further to
   allow predictions of the solar outbreaks.