What is space weather? In a few words space weather describes the highly variable state of the solar and cosmic radiation field, the interplanetary field and the near-Earth space environment that can diminish the performance and reliability of space and ground-based technological systems and can endanger human life and health.
Space weather effects cover a broad spectrum: they include electronic failures, immediate and long-term hazards to astronauts and aircraft crews, charging in satellites, distortions in telecommunication and navigation satellite systems, power transmission failures and disruption to rail traffic. In particular new space borne and ground based technological systems will most likely be more vulnerable to space weather effects.

The most striking feature of solar radiation is their cyclic variation over approximately 11 years. As predicted by solar physicists, the current solar maximum appears 2000/2001. During this time the scientists expect an enhanced occurrence probability for serious distortions in space weather starting e.g. as coronal mass ejections (CME's) from the sun and then propagating towards the Earth where complex coupling processes with the magnetosphere, ionosphere and thermosphere are initiated.
In addition to optical and particle radiation measurements also radioastronomical methods can effectively be used to monitor solar activity e.g. by the radiospectralpolarimeter (40-800MHz) of the Astrophysical Institute Potsdam. For aspects of the space weather event on 6 April 2000 click HERE.

To avoid or reduce the above mentioned space weather induced hazards, there is a growing request for reliable forecasts of hazardous space weather events for manned space activities, for unmanned spacecrafts, for space and ground-based industry, for the public and insofar for many aspect of daily life.
Since space weather effects can cause a serious impact on present and future global satellite navigation systems, the Institute for Communication and Navigation (IKN) of DLR is principally interested in this area.
Space based navigation and positioning is mainly influenced by the interaction of navigation signals in the L-band frequency range with free electrons in the ionized part of the Earth's atmosphere, called ionosphere. The global behavior of the ionosphere is strongly controlled by typical space weather perturbations such as solar flares or geomagnetic storms.
In particular strong gradients and irregularities in the electron density structure of the ionosphere reduce the accuracy and reliability of space based navigation systems such as GPS and GLONASS. To reduce the impact of space weather on operational navigation systems, solar radiation and the ionospheric ionization have to be monitored in near real time and should be predicted at least some hours ahead.
The Total Electron Content (TEC) of the ionosphere can effectively be monitored by using ground (see TEC maps) and space-based ( CHAMP) GPS measurements. For application in operational navigation satellite systems the monitoring data have to be processed in a near-real-time mode.
While U.S.A. and Japan already establish national Space Weather programs, Europe (ESA) is studying needs and benefits of a potential Space Weather Program. Such a program should include a number of activities such as research of solar-terrestrial relationships, development of models and forecasting methods, operational monitoring and forecasts, maintenance of a permanent service for the broad user community, education and training of users.
To raise public awareness on space weather in Europe, the EU has started a project called "Space Weather" that shall show people, organisations, industry and governments the impact of space weather on every day life.  The project consortia will organize  a space weather forum and a travelling exhibition within  the European Science and Technology Week (ESTW, 4 - 10 November 2002). Further on an interactive CD-Rom and a video shall be produced (WWW Greifswald).