The Sun, the solar wind and the heliosphere

The Sun’s outer atmosphere, the solar corona, can be observed with unaided eye since ancient times during a total solar eclipse. Modern instruments give a permanent view on the Sun which allows us to study not only the visible (white-light) structure of the corona above the limb of the Sun, but also features on the solar disk by using other spectral ranges. Due to the enormous temperatures, the corona is highly structured and dynamic having a continuous outflow, the solar wind, which fills the space between the Sun and its planets. The Sun changes its magnetic field and activity over a period of about 11 years, the so-called solar cycle. During the solar cycle, the appearance and occurrence of magnetically related structures and events, such as sunspots, CMEs, flares, coronal holes, solar wind etc. change dramatically on spatial and temporal scales (Schwenn, 2006). Slow solar wind, forming above active regions, together with high-speed solar wind streams (HSSs), emanating from coronal holes, and sporadic fast flows of coronal mass ejections (CMEs) interact with each other shaping the distribution of solar wind flow in the inner heliosphere. With this, the environmental conditions of near-Earth space permanently change and form/influence our space weather (see e.g., Bothmer and Daglis, 2007). The strongest geomagnetic storms are caused when CMEs or HSSs interact with the Earth’s magnetosphere (e.g., Tsurutani et al., 2006). Due to the increased need and economic dependence on space technology it becomes more and more relevant to improve the knowledge of our space environment and to forecast space weather conditions.

Our services comprise forecasts of the solar wind speed, forecasts of the arrival time and impact speed of CMEs, as well as real-time alerts of solar flares.



Image courtesy: ESA