Figure 12: The normalized electric field components [[spi:math]] and [[spi:math]] and the corresponding current density components [[spi:math]] and [[spi:math]] computed for a 1 mV/m perpendicular electric field at the topside ionosphere with a perpendicular scale size of 10 km are shown as functions of altitude. For a topside field of, say, 30 mV/m the ordinates need to be proportionately scaled. It is seen that the currents of this scale size are shorted above 150 km and the fields do not penetrate to the lower atmosphere. Figure 13: Schematic illustration of Joule dissipation at the ionosphere as result of fields and currents driven by magnetospheric processes. Because the high-altitude field lines are essentially infinitely conducting, a magnetospheric potential drop across field lines appears also as an ionospheric potential drop. Figure 14: Altitude profiles of EUV and Joule heating rates per unit mass of the thermosphere. Since Joule heating rate depends on ionospheric density, two ionospheric conditions corresponding to high and low solar activity (Zurich sunspot numbers R=150 and R=50, respectively) are plotted. The imposed electric field is 10 mV/m. Figure 15: A comparison of the compositional structure of the plasmasphere under natural thermal conditions (left panel) and under heated circumstances (right panel). The natural H+ content at the 500 km altitude level is assumed to be unaltered. Ionospheric release of H2O may alter this assumption but in any case substantial fluxes of O+ are driven up to higher altitudes. Figure 16: Lowest-order estimates for the normalized growth rate as a function of normalized wave frequency, for various relative concentrations (NAr/NH) of argon and hydrogen plasma. The method of calcu88
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