It is generally accepted that the term space weather refers to the time-variable conditions in the space environment that may effect space-borne or ground based technological systems and, in the worst case, endanger human health or life. Therefore there are social and economic aspects of this type of research: one tries to avoid consequences of space weather events by system design or efficient warning and prediction. During the last few years space weather activities have expanded world-wide. Space weather affects spacecrafts as well as ground based systems. The main cause for space weather effects is our Sun. It emits a continuous stream of particles which is called the solar wind. The solar wind is variable. It is modulated by the well known 11 year solar activity cycle. Another source of space weather effects are micrometeorites and other space debris.