The term heliophysics was coined in 1981 to denote the physics of the entire Sun: from centre to corona. It is a direct translation from the French ‘he ?liophysique’, which was introduced to provide a distinction from physique solaire (solar physics) which in practice was then confined to only the outer layers of the Sun. It is a subdiscipline of heliology. Recently the meaning of the term has been extended by Dr George Siscoe of Boston University to include the physics of the heliosphere (the space around the sun beyond the corona, in principle out to the shock where the solar wind encounters the interstellar medium, but excluding the planets and other condensed bodies). It has subsequently been used by the NASA Science Mission Directorate to encompass the study of the heliosphere and the objects that interact with it—most notably, but not limited to, planetary atmospheres and magnetospheres, the solar corona, and the interstellar medium. Heliophysics combines several other disciplines, including several branches of space physics, plasma physics, and solar physics, including stellar physics in general.
Heliophysics is all of the science common to the field of the Sun-Earth connections. This fast-developing field of research covers many traditional sub-disciplines of space physics, astrophysics, and climate studies. The NASA Living With a Star program, with its focus on the basic science underlying all aspects of space weather, acts as a catalyst to bring the many research disciplines together to deepen our understanding of the system of systems formed by the Sun-Earth connection.
Earth moves through the heliosphere, the exotic outer atmosphere of a star. The space beyond Earth’s protective atmospheric cocoon is highly variable and far from benign. The Sun, our solar system, and the region of the galaxy just outside present us with a complex, interacting set of physical processes. It is the one part of the cosmos accessible to in situ scientific investigation, our only hands-on astrophysical laboratory.
Building on NASA’s rich history of exploration of Earth’s neighborhood and distant planetary systems, we are poised to provide a predictive understanding of our place in the solar system. We do not live in isolation; we are intimately coupled with the Sun and the space environment through Earth’s climate system, our technological systems, the habitability of planets and solar system bodies we plan to explore, and ultimately the fate of Earth itself. Variability in this environment affects the daily activities that constitute the underpinning of modern society, including communication, navigation, and weather monitoring and prediction. Because the space environment matters to humans and their technological systems both on Earth and in space, it is essential as a space-faring Nation that we develop an understanding of these space plasma processes.