Interaction of a localized shear Alfven wave with the anisotropic conducting ionosphere: Behaviour in a near-source region

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We present results of detailed numerical analysis of effects of the nonuniform, anisotropic conducting ionosphere on the localized shear Alfven wave, in assocation with the origin of pc-1 geomagnetic pulsations observed on the ground in high latitudes. Employing a simple four-layer model that consists of the evanescent magnetosphere for the fast magnetosonic wave, the ducting upper ionosphere, the E-layer with anisotropic conductivities, and the metallic earth, we obtain numerical solutions representing the behaviour of surface magnetic variations in a near-source region. The rate of spatial attenuation of the induced magnetic intensity at the ground varies with a horizontal distance from the center of the source, taking the same order of magnitude as that of the incident wave in the source region, but it becomes a smaller value over radial distances of an outside region. This deviation is attributed to the effects of trapped fast mode waves in the upper ionosphere, which can propagate to horizontal direction crossing vertical magnetic field lines. The major axis of polarization of the horizontal magnetic vector on the ground is nearly perpendicular to that of the incident wave, while its ellipticity and sense of rotation are almost the same as those of the incident wave.
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