The Sun and Heliosphere

Abstract

The Sun is our star. It provides the energy that makes life’s existence on Earth possible. The main zones of the observed Sun are the photosphere, chromosphere, and corona. Their composition, structure, and peculiarities are intrinsically related with the interior where nuclear fusion occurs. Solar activity includes an 11-year solar cycle and different phenomena caused by disturbances in the chromosphere/corona. The solar wind is a plasma flowing out permanently from the Sun. It fills up the region called the heliosphere, which surrounds the Sun and expands to a huge distance where its outer boundary interacts with the interstellar medium. Important phenomena within the heliosphere are solar wind interactions with the planets and small bodies, particularly interactions with the Earth’s upper atmosphere and magnetosphere, which protect the biosphere from harmful solar electromagnetic and corpuscular radiation.