We present mathematical modelling of the stationary geothermal field for the two-layered Earth which includes a three-dimensional perturbing body below the first layer (in the substratum). The body is in the form of 3D prismoid with sloping side faces, while its upper and lower face are rectangles at the planes z = z1, z2. The theoretical formulae are based on the generalized theory of the double-layer potential and boundary integral equation (BIE). Special attention is paid to the quadrilateral prismoids bounded by planar skew faces. The numerical calculations were performed for the 3D prismoids (blocks) with thermal conductivity different to the ambient substratum, while the upper face of the prismoid may be in contact with the upper layer. Numerous graphs are shown for the disturbance of the heat flow on the surface of the Earth or inside the first layer.

[1] The solar eclipse on 11 August 1999 was quite unique due to its totality belt coverage of the territory of central Europe where the facilities for the geophysical monitoring are most dense. Ionospheric and geomagnetic observations during the eclipse allowed us to study the eclipse-induced effects more precisely. A mathematical model based on the classical Ashour-Chapman model is considered to show that the decrease (up to 40%) of the ionospheric total electron content in the region of the totality belt leads finally to geomagnetic disturbances quantitatively dependent on the position of both the quasicircular spot of the ionospheric conductivity decrease and given geomagnetic observatory location. The model is generalized for the anisotropic ionosphere. The theoretical estimates are compared with observational data from European geomagnetic observatories: Fürstenfeldbruck, Nagycenk, Tihany, and Hurbanovo, the last one being nearby the totality belt.INDEX TERMS: 1517 Geomagnetism and Paleomagnetism: Magnetic anomaly modeling; 2409 Ionosphere: Current systems (2708); 2411 Ionosphere: Electric fields (2712); KEYWORDS: ionospheric currents, geomagnetic disturbance, eclipse effect, mathematical model Citation: Hvoždara, M., and A. Prigancová, Geomagnetic effects due to an eclipse-induced low-conductivity ionospheric spot,

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