of the Ar particles are physically present in the ionospheric end of the flux tube. After a time [[spi:math]] (Alfven wave transit time discussed in III.B) an elec- tric field [[spi:math]] is imposed on the topside ionosphere. This perpendicular electric field forces the ionospheric plasma into motion. Because of the finite conductivity of the ionosphere, a Pedersen current [[spi:math]] (45) flows in the ionosphere. According to our numerical model of beam-magnetosphere interactions [[spi:math]]. is about 30-80 mV/m for the Ar+ beam located at (2-4) RE. The magnitude of [[spi:math]] increases with lower beam altitude. Since [[spi:math]] is about the same as the observed auroral electric field, the ionospheric current driven by the Ar+ beam is expected to be similar to auroral currents, although it must be pointed out that the scale size (perpendicular dimension) of [[spi:math]]. is Xr considerably smaller (tens of kilometers). In the SPS atmospheric effects panel meeting in Chicago in 1978, the possibility of electrical coupling between the upper and lower atmospheres was considered to be a possibly consequential effect of the SPS. Since we have obtained [[spi:math]] from our modeling of the beam-magnetosphere interactions, we can proceed one step further and consider the electrical coupling between the lower ionosphere and the topside ionosphere, where [[spi:math]] is applied. To study the distribution of artificial ionospheric currents induced by [[spi:math]], one must "map'' the electric field through the various ionospheric layers, conserving the ionospheric current, by methods such as described in Chiu (1974). Since the conductivity inside the ionosphere is an anisotropic tensor, both parallel and perpendicular currents will be induced by [[spi:math]]. The 40
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