Magnetism lies at the root of most solar and heliospheric physics.
In terms of pure science, solar magnetism provides the Rosetta stone of cosmic magnetism, not only in other stars but also in accretion disks, cataclysmic variables, galactic dynamics, active galactic nuclei and other cosmic objects in which MHD and plasma processes control the structure and energy partitioning. The sun is close enough to study these processes in observable detail. Terrestrial plasma confinement machines do not reach the scales, densities and temperatures exhibited in the solar atmosphere. Solar physics complements plasma instability studies in fusion research, the sun representing a non-terrestrial plasma physics laboratory. Solar activity modulation affects satellite orbits, influences jet stream patterns and contributes to the causes of minor, possibly major, ice ages.