The Sun is the closest star and essential for living things to grow on the Earth. It is a fundamental human desire to know more about the Sun.

We have a big motivation to research the Sun. The Sun is the only celestial object in the big Universe for which we can perform detailed observations of the phenomena occurring now. It is thought that more than 99 percent of the phenomena which happen anywhere in the Universe may also occur in the Sun, so learning about the Sun is a good way to understand about the Universe. As the leader of the Solar System, the Sun affects our environment and our activities in it. So if we consider the Sun and interplanetary space extending from it to the far end of the heliosphere as an integrated system, it is important to understand solar activity as the source of energy in this system. And finally, the Sun is a big laboratory in space that shows us experiments we cannot perform on the Earth.