Remote sensing the earth's plasmasphere

The plasmasphere is a doughnut-shaped plasma cloud that surrounds the Earth to an equatorial distance of several RE (see, for example, [1], and references cited therein). Consisting primarily of cool (∼1 eV) H⁺ ions and electrons, supplemented by smaller populations of He⁺ and O⁺, it acts in part as a high-altitude extension of the Earth's regular (< 1000 km altitude) ionosphere. As an element of the Earth's space weather system, it is subject to substantial changes during storm-like disturbances in space induced by solar activity. Figure 1 shows the location of the plasmasphere with respect to other features of the Earth's space environment, in cartoon fashion.