parallel electric field so generated within the ionosphere "short-circuits” the current imposed by [[spi:math]] and prevents the field to be transmitted further into lower ionosphere. This short-circuiting phenomenon depends, however, upon the perpendicular scale size of the electric field [[spi:math]]. The smaller the scale size, the higher up in the ionosphere the short-circuiting phenomenon takes place; and consequently, electric fields of small scale size cannot penetrate the ionosphere to lower altitudes. In FY80, we have applied the ionospheric electric field mapping program of Chiu (1974) to the SPS electric field induced by the Ar+ beam. The scale size of the Alfven wave electric field in the magnetosphere is about two argon gyro radii (Fig. 1), but because of the convergence of the flux tube, the scale size of [[spi:math]] is smaller but in the range of tens of kilometers. From Figure 12, it is seen that [[spi:math]] of tens of kilometer scale size are unlikely to penetrate the ionospheric layers to the bottomside ( ~ 100 km), so we do not expect the induced electric field [[spi:math]] to be an important source of atmospheric electric field disturbances, since it would be dissipated in thermospheric heating. C. Thermospheric Heating Even though the induced ionospheric current cannot penetrate to the lower ionosphere, the energy dissipated by Joule heating can be of considerable consequence in heating the thermosphere. In FY80, we have evaluated this artificial source of thermospheric heating. For comparison, we have also evaluated the normal EUV absorption heat source of the thermosphere. Consider a weakly ionized ternary atmosphere for which we denote the number density Nj and mass mj of species j, running through the neutrals (n), ions (i) and electrons (e). Under the influence of an electric field [[spi:math]] in 41
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