Researchers have never been so well prepared to study the complete life cycle of this type of complex and important natural event. The past 15 years have also produced explosive growth in our knowledge of our Sun's outputs and the responses of Earth's atmosphere to them. As noted above, significant progress has been made in understanding the solar cycle and shorter-term variations of the particle and field outputs of the Sun, including the solar wind and solar energetic particle fluxes. The different consequences of flares and CMEs on the Sun, in interplanetary space, and at Earth are beginning to be understood. Yet the physical means by which these different aspects of solar variability affect Earth's atmosphere are as diverse as their own underlying solar sources.
Several examples serve as the best illustration.
However, how the Sun's magnetic field establishes the degree of imbalance of these two magnetically controlled features remains unknown. These total irradiance variations are the solar variations most likely to directly affect Earth's climate over long time frames. A second example relevant to the relationship between the Sun and Earth's climate concerns the possible role of the ionization state of Earth's atmosphere, which is known to affect its chemistry, its response to solar wind disturbances of the magnetosphere, and other processes that depend on the presence of free charges. Although this state is mainly controlled by the solar UV and EUV flux responsible for the ionosphere proper, some deeper ionization is produced by solar x-rays, solar energetic protons, and galactic cosmic rays. The flux of galactic cosmic rays at Earth and other solar system bodies is known to be reduced during periods of high solar activity.