 A considerable percentage of these ions remain bound inside Earth's magnetic field, where they form part of the radiation belts.The term was coined in 1968 in a pair of articles by Banks and Holzer and by Ian Axford.Since the process by which the ionospheric plasma flows away from the Earth along magnetic field lines is similar to the flow of solar plasma away from the sun's corona (the solar wind), Axford suggested the term "polar wind."