Shortly before the beginning of the space age, Eugene N. Parker of the University of Chicago predicted that interplanetary space would be filled with a plasma flowing rapidly outward from the Sun (Parker 1958). The likelihood that the Sun ejects charged particles that cause auroral and magnetic activity on Earth was generally accepted by that time. The observation that the plasma tails of active comets always point almost radially away from the Sun led Ludwig Biermann (1951) to postulate that the solar corpuscular radiation is continuous, rather than intermittent.It was also known that the outer atmosphere of the Sun, the solar corona, was extremely hot, with a temperature exceeding a million degrees. Sidney Chapman (1957) calculated that if the corona was in hydrostatic equilibrium, it must extend throughout the Solar System and cool off to only ~2 × 105K at the orbit of Earth. Parker (1958) put all these ideas together, explaining that the inward pressure of the interstellar medium was too weak to allow the solar atmosphere to be in hydrostatic equilibrium. He coined the phrase “solar wind” to describe the outward flowing solar Corona which supplies the pressure required to stand off the local interstellar medium, to exert the necessary force on cometary plasma tails, and to transmit solar disturbances to the geomagnetic field